Is it possible to use Google Voice Visual Voicemail? If so, how do I set it up?
Are you on Verizon? Do you have a Google Voice number? Did you download the Google Voice app?
If so, open up the phone app, dial *71AAANNNNNNN, and press the call button where AAANNNNNNN is your Google Voice area code and phone number.
This command will tell Verizon's system to forward your calls to Google Voice when they're not picked up (either no answer, out of coverage, or rejected).
Go to the Google Voice website (voice.google.com) to set up your greetings, etc.
I have several "Interesting Calendars" set up in my Google Calendar to show my favorite sports teams' schedules but these calendars are not showing up on my phone, how do I fix that?
Calendar > ... in the upper right corner > Settings > your email address, and check the calendars you want to sync. Or if they're already synced, Calendar > ... in the upper right corner > Calendars to Display, check the ones you want to display.
Where can I find 1440x1280 wallpapers?
I'm also looking for some good ones for the phone.
When I'm at my friend's house or a point of interest how do I save my location for future use in the Nav app? How can I automatically add my friend's address to their contact info?
That would be a cool feature, but I don't think it can be done right now. The most you can do is long press a location on the map, tap it, and Star it, by tapping the star icon in the upper right.
It then goes into My Places, which is easily accessible in the Maps menu. There's also a tab in My Places called Recent which keeps recent addresses you were at, and you can add those as Contacts, but I think it only looks for businesses and other locations with names.