It seems that most people aren't aware of the huge amount of quality manga available so I figured I would make a list to help show people what is out there. All of these are at least partly available in English, but some are only available via scanlation. I've shown which ones are licensed in English so please buy what you can.
If there is anything you feel is missing just tell me and I'll add it.
So everyone go look at the list read what looks interesting and post your impressions in the Manga Thread (which isn't just for weekly shounen manga!).
Other Recommendations
Basara
Kodomo no Omocha
Kare Kano
Kenji
Afterschool Charisma
Eden
Guyver
Gokusen
Not Simple
Inugami
Sayonara Zetsubo Sensei
Five Star Stories
Rokudenashi Blues
Crows
Worst
Adventures of Young Det
Suikoden III
Gyo
Museum Of Terror
Inugami
Kaiji
Akagi
Ten - Tenna Toori no Kaidanji
Gambling Emperor Zero
Buraiden Gai
Seizon - Life
Detroit Metal City
Amanchu
World Embryo
Franken Fran
The Kurosagi Corpse Delivery Service
River's Edge
Ikigami
Monster Collector
My Year
Team Medical Dragon
Emma
Otoyomegatari
Shirley
Tokyo Zombie
Keiko Ichiguchi America
Saint Young Men
Blade of the Immortal
Mahoraba
Shigurui
King of Thorn
Chatting over at the Amber Teahouse
2001 Nights
Drifting Classroom
Love Roma
Banana Fish
Phoenix
Shadow Star
Subaru
Witches by Daisuke Igarashi
Children of the Sea by Daisuke Igarashi (Licensed)
Hanashippanashi by Daisuke Igarashi
Goodnight Punpun by Inio Asano
Solanin by Inio Asano (Licensed)
Nijigahara Holograph by Inio Asano
What a Wonderful World by Inio Asano (Licensed)
Tekkonkinkreet by Taiyo Matsumoto (Licensed)
Ping Pong by Taiyo Matsumoto
Hanaotoko by Taiyo Matsumoto
Takemitsu-Zamurai by Taiyo Matsumoto
Gogo Monster by Taiyo Matsumoto (Licensed)
Japan Tengu Party Illustrated by Iou Kuroda
Sexy Voice and Robo by Iou Kuroda (Licensed)
Nasu by Iou Kuroda
MW by Osamu Tezuka (Licensed)
Ode to Kirihito by Osamu Tezuka (Licensed)
Buddha by Osamu Tezuka (Licensed)
Freesia by Jiro Matsumoto
Tropical Citron by Jiro Matsumoto
Uncivilized Planet by Jiro Matsumoto
Touch/Rough/H2/Katsu/Cross Game by Mitsuru Adachi (Cross Game is Licensed)
Adachi's manga all pretty much follow the same basic formula with a nice blend of sports, romance and comedy.
Real by Takehiko Inoue (Licensed)
Vagabond by Takehiko Inoue and Eiji Yoshikawa (Licensed)
Monster by Urasawa Naoki (Licensed)
20th Century Boys/21th Century Boys by Urasawa Naoki (Licensed)
Pluto by Urasawa Naoki (Licensed)
Billy Bat by Urasawa Naoki
Takehiko Inoue, Mitsuru Adachi and Urasawa Naoki are pretty well known, but they're awesome so I listed them anyways.
If there is anything you feel is missing just tell me and I'll add it.
So everyone go look at the list read what looks interesting and post your impressions in the Manga Thread (which isn't just for weekly shounen manga!).
Other Recommendations
Basara
Kodomo no Omocha
Kare Kano
Kenji
Afterschool Charisma
Eden
Guyver
Gokusen
Not Simple
Inugami
Sayonara Zetsubo Sensei
Five Star Stories
Rokudenashi Blues
Crows
Worst
Adventures of Young Det
Suikoden III
Gyo
Museum Of Terror
Inugami
Kaiji
Akagi
Ten - Tenna Toori no Kaidanji
Gambling Emperor Zero
Buraiden Gai
Seizon - Life
Detroit Metal City
Amanchu
World Embryo
Franken Fran
The Kurosagi Corpse Delivery Service
River's Edge
Ikigami
Monster Collector
My Year
Team Medical Dragon
Emma
Otoyomegatari
Shirley
Tokyo Zombie
Keiko Ichiguchi America
Saint Young Men
Blade of the Immortal
Mahoraba
Shigurui
King of Thorn
Chatting over at the Amber Teahouse
2001 Nights
Drifting Classroom
Love Roma
Banana Fish
Phoenix
Shadow Star
Subaru
Witches by Daisuke Igarashi
A wildly imaginitive trek into the deepest realms of human beliefs and the mysteries of the universe. Daisuke Igarashi's amazing pen can recreate anything he can imagine on paper, resulting in beautifully chaotic, maddeningly detailed scrawls of pure wonder. A true celebration of the human imagination.
When deep emotions come to the head, the witch that dwells in the heart awakens - the gorgeous and literary illusory tales begin.
Witches won the Excellence Prize in the Manga Division at Japan Media Arts Festival in 2004.
Children of the Sea by Daisuke Igarashi (Licensed)
One summer vacation, Ruka meets two boys, "Umi" and "Sora," whose upbringing contains strange and wonderful secrets. Drawn to their beautiful swimming, almost more like flying, Ruka and the adults who know them are intertwined in a complex mesh...
Meanwhile, an unexplained anomaly is occurring all over the world: fish are disappearing. Thus begins a marine adventure of boys and girls to captivate all the senses!
Children of the Sea won the Excellence Prize in the Manga Division at Japan Media Arts Festival in 2009.
Hanashippanashi by Daisuke Igarashi
A collection of short stories about supernatural occurrences that take place in our everyday
Goodnight Punpun by Inio Asano
Witness the titular Punpun - who is depicted as a tiny, caricatured bird in an otherwise normal human setting - as he copes with his dysfunctional family and friends, his love interest, his oncoming adolescence and his hyperactive mind.
Solanin by Inio Asano (Licensed)
Slice of life with a young couple, Inoue Meiko and Taneda Shigeo, and how everyday occurrences affect their lives. Meiko begins contemplating whether freedom without purpose is really the same thing as boredom. This is a retelling of a very common real life situation, perhaps enjoyable for an older fanbase. Art is different, there are no anime-esque deformations here.
Nominated in 2009 for the Eisner Award Best U.S. Edition of International Material - Japan. Nominated for the 2009 Harvey Award for Best American Edition of Foreign Material.
Nijigahara Holograph by Inio Asano
Suzuki is a troubled boy. He's lived with uncaring foster parents for most of his life, alienated from the other kids at his school, owner of a cynical, unhappy mentality. Komatsuzaki is a violent, unpredictable bully whose head trauma causes him to act in mysterious, inexplicable ways. Arakawa is a no-nonsense, normal girl who pines after Komatsuzaki but can never have him. A teacher with just one working eye. A mother who committed suicide. A daughter in an endless coma. Attempted rapes, murders, extortion, sexual deviance, and a freakish explosion in the butterfly population. All of these elements are whirled together in a story spanning 10 years, a tale of blackness, pain, and apocalypse. And maybe just a bit of hope and redemption. It's a spiritual cross between the misanthropic suburban malevolence of Kyoko Okazaki's Rivers Edge and the eerie mysticality of Donnie Darko.
What a Wonderful World by Inio Asano (Licensed)
Being his first series, What a Wonderful World remains Asanos most representative and successful work to date.
Composed of vignettes from the daily lives of a group of people inhabiting an ordinary neighborhood somewhere in Tokyo, the series is actually a comment about modern life itself and how we can survive in it despite all its rigors.
Amusing, melancholic, funny, strange, thought-provokingAsano effortlessly shifts from one mood to another, creating stories and characters that are profoundly human and thus always involving. Its a shame that not everyone will find the subjects the author describes equally appealing since some of them are distinctly Japanese. But overall, its a great collection that any discerning manga reader should check out.
Tekkonkinkreet by Taiyo Matsumoto (Licensed)
Orphaned on the mean streets of Treasure Town, lost boys Black and White must mug, steal and fight to survive. Around them moves a world of corruption and loneliness, small-time crooks and neurotic police officers, and a band of sadistic yakuza who have plans for their once-fair city. Can they rise above their environment?
Ping Pong by Taiyo Matsumoto
Ping pong. Table tennis. Fast, furious. You might have seen it, even played it, but you've never seen it like this! The action centers around "Smile" Tsukimoto and "Peco" Hoshino, two high school students in the midst of adolescence and out to prove they've got what it takes in the cool, cruel world of sports.
Hanaotoko by Taiyo Matsumoto
Shigeo is a high strung elementary school student living with his mother. His only concern is getting ahead in life by doing well in school. He despises his father Hanao (who is separated from them), who's an idealistic free spirit and a kid at heart, infatuated with the sport of baseball. Shigeo's mother forces Shigeo to take time to visit his father, and so begins Shigeo's lessons that there's more to life than excelling academically (courtesy of his very childish father).
Takemitsu-Zamurai by Taiyo Matsumoto
Early one New Year's morning, the ronin Senou Souichirou shows up in the Katagi tenements in Edo. He is a suspicious figure. Kankichi, the carpenter's son, thinks he may not be human. But soon enough he has pawned his sword, and settled down into the life of the community.
All is well for a time. Only troubles will not leave the Katagi tenements alone ...
Gogo Monster by Taiyo Matsumoto (Licensed)
The emotional tale of a young boy's overactive imagination during school.
Taiyo Matsumoto drew this completely on his own, and released it as a standalone volume, rather than having it serialised in a manga anthology.
Japan Tengu Party Illustrated by Iou Kuroda
A tengu is an utterly proud and arrogant creature (so much that the Japanese saying, "to become a tengu," means to preen conceitedly) that is said to steal young children away from their homes. In this story, the fractured and disgraced remnants of the tengu species come together from all over the country to rise up, reclaim their pride, and rule over the nation of Japan, as is their right. What kind of effect will the "Tengu Party" have on the humans of Japan, and more importantly, what exactly makes a tengu?
Sexy Voice and Robo by Iou Kuroda (Licensed)
She calls herself Sexy Voice. To most of the world, she's just Hayashi Niko, an ordinary schoolgirl - but when time permits, she lives a double life as a hired investigator/spy. To help her, she has recruited the rather unlikely assistant she calls Robo, a geeky lump of a man who doesn't really know why he feels the need to do everything she tells him to. He just does it. Together, the odd team solve a number of cases for Sexy Voice's employer, an aging gangster.
Nasu by Iou Kuroda
Short stories all related through a common medium: Eggplant.
MW by Osamu Tezuka (Licensed)
Gurai is a Japanese Catholic Priest, who is unable to give up his lifelong sexual relationship with Yuki, a beautiful and sadistic young master criminal. Yuki's malicious crimes have become more and more extreme over the years, claiming many innocent lives, and Gurai is tormented by guilt at his inability to stop them
Ode to Kirihito by Osamu Tezuka (Licensed)
Two young doctors, the passionate and well-liked Osanai and the ambitious Tatsugaura, are both investigating the mysterious 'Monmo' disease, found only in one remote village, which causes bizarre bone deformation, making its victims take on a beastlike appearance before their deaths. Osanai, caught between the allure of his urban medical world and the rural peace offered by the remote village, does his best to help the victims retain their humanity in the face of a medical establishment which views them only as guinea pigs and oddities. Meanwhile, Tatsugaura schemes against Osanai and tries to infect his rival with the disease in order to gain fame from researching the results.
Buddha by Osamu Tezuka (Licensed)
The complete biography of Buddha, as seen by Osamu Tezuka.
Received the Bungei Shunju Manga Award in 1975 and ended in 1984.
Freesia by Jiro Matsumoto
Freesia is set in an alternative Japanese society that is at war, and has passed a law legalizing retaliatory killings. If somebody kills your loved one, you are legally sanctioned to kill, or hire someone to kill, the victimizer. The manga is set around a character who works for a firm that specializes in these retaliatory killings.
Tropical Citron by Jiro Matsumoto
A coming-of-age story about a young, aspiring photographer named Soma. He's going nowhere, stuck in a mire of sex and drugs, until a horrible end to a one night stand sets him on a path that changes his life forever.
Uncivilized Planet by Jiro Matsumoto
From Jiro Matsumoto (the author of Freesia) comes a story of three childhood friends - Nicolo, Cookie, and Naomi - who grew up in a sleepy backwater town on an uncivilized planet. They struggle to get by while holding on to their dreams of leaving town and finding a better life... but can their friendship endure the tests of time? Can it withstand invading armies, broken dreams, conflicting ambitions, divided loyalties, jealousy, and even betrayal?.
Touch/Rough/H2/Katsu/Cross Game by Mitsuru Adachi (Cross Game is Licensed)
Adachi's manga all pretty much follow the same basic formula with a nice blend of sports, romance and comedy.
Real by Takehiko Inoue (Licensed)
The story revolves around three teenagers: Nomiya Tomomi, a high school dropout; Togawa Kiyoharu, an ex-sprinter who now plays wheelchair basketball; and Takahashi Hisanobu, a popular leader of the high school's basketball team who now finds himself a paraplegic after an accident.
Real features a cast of characters who find themselves being marginalized by society, but are all united by one common feature: a desire to play basketball, with no place to play it in. Nomiya, being a high school dropout, has no future in his life. Togawa, being a difficult personality, finds himself constantly feuding with his own teammates. Takahashi, once a popular team leader, now finds himself being unable to move from the chest down.
Real also deals with the reality of physical disabilities, and the psychological inferiority that the characters struggle against. The characters break through their own psychological barriers bit by bit.
Vagabond by Takehiko Inoue and Eiji Yoshikawa (Licensed)
Striving for enlightenment by way of the sword, Miyamoto Musashi is prepared to cut down anyone who stands in his way. Vagabond is an action-packed portrayal of the life and times of the quintessential warrior-philosopherone of the most celebrated samurai of all time!
Vagabond portrays a fictionalized account of Miyamoto Musashi's life, on a loose adaptation of Eiji Yoshikawa's novel "Musashi".
Vagabond won the Grand Prize for manga at the 2000 Japan Media Arts Festival. The same year, Vagabond won the 24th Kodansha Manga Award in the general category. Vagabond also received the highly-acclaimed Tezuka Osamu Cultural Prize in 2002.
Monster by Urasawa Naoki (Licensed)
Monster weaves the riveting story of brilliant Dr. Kenzo Tenma, a famous surgeon with a promising career at a leading hospital. Tenma risks his reputation and promising career to save the life of a critically wounded young boy. Unbeknownst to him, this child is destined for a terrible fate. A string of strange and mysterious murders begin to occur soon afterward, ones that professionally benefit Dr. Tenma, and he emerges as the primary suspect. Conspiracies, serial murders, and a scathing depiction of the underbelly of hospital politics are all masterfully woven together in this compelling manga thriller.
The series won an Excellence Prize at the 1997 Japan Media Arts Festival and the Shogakukan Manga Award in 2001.
20th Century Boys/21th Century Boys by Urasawa Naoki (Licensed)
Growing older is pretty rough and Kenji is finding out just how hard it can be as life starts wearing down on him. On top of trying to make ends meet running a convenience store, he has to care for the niece that his missing sister left in his care. Memories of youth make it easier, until those memories come back to haunt you.
Kenji and his old friends are slowly being drawn into a mysterious conspiracy that could threaten the world. Who is the mysterious "friend", and how does he tie into Kenji's youth? Why are there disappearances and deaths tied into Ochanomizu University? The friend's memories hold the keys to the puzzle, but years between cloud the clues.
The strange occurances and the reach of the "friend" conspiracy grow by the day. It will all culminate on New Year's Eve 2000. Will Kenji and the rest of the group be able to put together the puzzle and save the world?
20th Century Boys won the 2001 Kodansha Manga Award in the General category, an Excellence Prize at the 2002 Japan Media Arts Festival, and the 2003 Shogakukan Manga Award in the General category.
Pluto by Urasawa Naoki (Licensed)
A murder occurs without any trace of human beings, and with only a mysterious message remaining. What will follow!? Two great Japanese manga artists come together to make this near-future science-fiction suspense manga!!
Pluto received an Excellence Prize for manga at the 2005 Japan Media Arts Festival. The series also received the 2005 Tezuka Osamu Cultural Prize Grand Prize.
Billy Bat by Urasawa Naoki
Billy Bat is a comic-in-a-comic and the real protagonist is a Japanese-American artist named Kevin Yamagata who draws Billy Bat for "Marble Comics".
Shortly after they transition to the artist in his studio with his assistant, two actual detectives, who look like Laurel and Hardy in Dick Tracy era suits and trench coats, knock on the door and appropriate Kevin's room for the purpose of conducting surveillance on a room in an adjacent building. One of the detectives, the skinny Laurel, sees Kevin's work and it turns out he's a Billy Bat fan. The other chubby "Hardy" detective picks up a page and says that the characters look familiar and accuses Kevin of translating an old "Jap" comic.
As Hardy remembers the comic he thinks Kevin is ripping off, we make another Urasawaesque time jump to 1949 Tokyo and the chapter ends.
Takehiko Inoue, Mitsuru Adachi and Urasawa Naoki are pretty well known, but they're awesome so I listed them anyways.