Free Music

Purple Planet:  Royalty free music for all.
www.purple-planet.com

Freesound:  A collaborative database of Creative Commons Licensed sounds. Browse, download and share sounds.
www.freesound.org

Incompetech:  Royalty-Free Music
www.incompetech.com/m/c/royalty-free/

Pandora:  Its a new kind of radio station that plays only the music you like
www.pandora.com