As mentioned, the short answer is "all of them", so it's just a matter of determining what order you'd like to watch them in. Here are a few brief descriptions that may help:
First off, the films of Isao "Nobody's Second Fiddle" Takahata:
Grave of the Fireflies - The tragic tale of two orphans trying to survive near the end of World War II. As expected, this is an emotional kick in the teeth. There are people out there who say they're unaffected by this film, but I don't believe them.
Fun Trivia Fact: Grave of the Fireflies was originally shown as a double feature with My Neighbor Totoro.
Only Yesterday - A very mellow film about a young urban office worker who goes to visit her brother-in-law's family in the countryside. The film alternates between her experiences of the countryside as a lifelong city girl and flashbacks her her childhood in Tokyo during the late 60s. The end result combines boatloads of nostalgia with a gentle romance and is absolutely wonderful to behold.
Tanuki Pom Poko - Japanese folklore versus urban modernization: the final battle! As Tokyo expands into the countryside a group of tanuki (a sort of racoon-like critters) realize theri homeland is vanishing and vow to fight back. Cue wacky, if desperate, tanuki hijinx, based on folklore about their shape-changing abilities and magic testicles. I shit you not. This sounds a bit odd, but it's a delightful film, with tons of humor, fantastical visuals, and a bit of reflection on the consequences of urbanization.
It also has one hell of an ending theme.
My Neighbors the Yamadas - Slice-of-life adventures of an average, endearing Japanese family based on a four-panel gag manga. There's not an overarching story per se, just lots of little tidbits, all animated with a wonderful watercolor effect. It's generally very lighthearted, though the father's Kamen Rider scene is a powerful, subtle exception. Great fun, in a gentle sort of way.
Takahata rocks the house. However, don't overlook the three Ghibli films that neither he nor Miyazaki directed:
I Can Hear The Sea - Also known as Ocean Waves, this is a saga of teenage romance directed by Tomomi "Here is Greenwood" Mochizuki. It's a nice little TV movie, with plenty of humor, low-key angst, and unrequited love, all centered on a junior highschool school trip. It's quite well done, though it doesn't hurt that I really dig Mochizuki's style. This wins my vote for the most overlooked Ghibli film, so buck the trend and check it out.
Whisper of the Heart - Quite possibly my favorite Ghibli film, Whisper of the Heart is a teenage love story that celebrates the joys of urban life in Tokyo. She's a voracious reader, he's a violin maker who's been checking out the same books, and there's romance, a bit of urban exploration, and novel writing. There's also a delightful fantasy sequence, adventures with cats both real and imagined, and more "Country Road" per second than any other feature film. Okay, so I'm not a fan of the ending line (you'll understand when you see it; it's changed from the original manga, and not for the better) but the rest of the film is just plain great. This was directed by Yoshifumi Kondou with lots of involvement by Miyazaki, with the idea that Miyazaki would retire and Kondou would become one of the major Ghibli directors. Alas, Kondou died a few years later, but he certainly left us with one helluva film.
The Cat Returns - Sheer delightful fluff for fans of Whisper of the Heart, this is the story of a young woman who finds herself drawn into the secret world of cats, with plenty of adventure and derring-do from The Baron and Moon from Whisper. This isn't what you would call a substantial film, but it's certainly entertaining, and available cheap thanks to the recent R1 release.
And there you have it. All of the R2 editions are quite swank and have English subtitles, so don't hesitate to pick up the entire Ghibli library. Enjoy!
FnordChan
