This is the best site out there for guitar (and bass) tabs by far:
http://www.songsterr.com/
The best thing about it is that it has rhythm notation to go along with the regular tabs, and each song has a corresponding MIDI track so you can see exactly what notes you're supposed to be playing when. The song selection isn't as good as the OLGA (before it was sued into shutting down) or sites like ultimate-guitar.com, but you'll find most popular well-known hits there.
[Edit]
Beaten by Delthefunky!