david over at Largehearted Boy (a great music blog), has put together a page with literally dozens of legal video and MP3 downloads from Bonnaroo 2008.
david's done alot of hard work consolidating all these files in one place. He's got everything from the Derek Trucks Band to Metallica, Pearl Jam, Phil Lesh and Friends, and The Raconteurs. In fact, there's even a set by Willie Nelson.
No Kanye yet.
(On a related note: As of this post, I've broken my unspoken vow to never mention Metallica on this blog.)