The South By Southwest Music Festival has made available a whole bunch of MP3s from the artists performing there. Over 48 hours of music, 756 files, 2.6 GB. If you have broadband, there's some good stuff in there. The web page describes it as being all for iPod, but if you just unzip the files they're all MP3s.

Details:
http://2005.sxsw.com/geekout/fest4pod/

Torrent:
http://player.sxsw.com/SXSW_2005_Sho...t_mp3s.torrent

For those of you who have never used BitTorrent, the official client is available at www.bittorrent.com. It's absolutely critical that you forward a small (configurable) range of ports to it if you're behind a NAT, or your download speeds will suck.