Most every book by Hal Leonard publishing is great. Their transcriptions are very accurate.
Sheetmusic.com is a good source.
Except for very simple songs, most of the free tabs on the net are crap.
For jazz Jamie Abersold is the best.
http://aebersold.com/Merchant2/merch...ry_Code=GUIBOO
Get some kind of recording setup. Even if it is a really crude low fidelity rig, it helps a lot to listen to yourself on playback.
The best thing to do if find something you like that is hard to play, get the book and learn to play it. Or is you have the ear, teach yourself from the CD.