Free Live Music Downloads
The Live Music Archive from archive.org offers hundreds of live concert audio for download free of charge, cd quality (FLAC), and 100% legal.
Some mainstream bands include: G. Love and the Special Sauce, Gin Blossoms, Grateful Dead, Los Lonely Boys, Maroon 5, Zwan (Billy Corgan from Smasing Pumpkins), Tenacious D (Jack Black) . There are lots more bands on there that are not mainstream that are very good too!
Got to love archive.org!