I highly recommend getting into Transcribing - using your own ears to work out the chords. But when you start out it can be helpful to get some clues from tab sites and get a rough idea about what is going on (or if there is a funny tuning or something like that!) before you get started.
Accuracy can vary a huge amount, some tabs are very accurate, some are just completely wrong, like not even close, so don't forget to USE YOUR EARS!
Free and good...
These are some sites that I think are a bit above the rest.
Good selection of tabs (over 21,000 at time of writing) with a player. very cool.
Free TAB sites
Does it have a rating system? Is it well organised?
Easy to find songs/artists with a user rating system.
A huge selection of tabs, a rating system, and a affective search engine.
Over 300,000 user rated tabs plus reviews and lessons.
Simple and clear tab site with a top 100 of the most popular song tabs.
Straight forward tab site with a helpful user rating.
All Guitar Tabs
Simple tab site that has easy to find midi versions.
Slightly over complicated tabsite but you'll find all the tabs you need there .
Clearly defined tab searches with a constantly updating list of new tabs.
Artist Specific TAB sites
There are some sites on the interweb that have tabs for a specific artist - I find these ones are usually more accurate than just the random tab sites, because they are usually done by people that love the music.
Sweet Adeline has lots of info on tunings and chords and tabs for solos and stuff. Very comprehensive, but accuracy varies between tabs.
John Mayer Tabs
Each of John's albums has been tabbed with some of the tabs in video/audio format.
Some of Hendrix's albums tabbed.
Free TAB developers
This area is for people developing new ways of presenting TAB.
Really cool tabs that syncs with video! some of my tunes have this feature...