These days gtptabs.com is my first stop when I'm looking for tab. It's a pretty good database, but it's all in GuitarPro format, so you'll need to download TuxGuitar, or some other program that can run gp files.
A lot of the GuitarPro-style tab editors have the capability to automatically generate tab from midi files too. So if you can find a midi version of a song, you can get tab for it that way.