http://beta.grooveshark.com/home.php



In addition to Free Play Music, here is another site you might try for use with multimedia projects.
http://www.kitzu.com/
kitZu is a a collection of free, educational, copyright-friendly media resources. Students and teachers around the world can access pre-made collections, or "kits," of various digital assets - still images, background music, narratives, video and text.

Possible sources for royalty free music content (check for creative commons license)

http://connectedlibraries.pbwiki.com/Valenza's+Copyright+Free+Multimedia+Links
http://creativecommons.org/audio
http://podsafeaudio.com/
http://www.setoncchs.com/library/music-online.htm
http://music.download.com/
http://www.kennedy-spaien.com/looking-at-podsafe-music-and-the-public-domain-for-your-show
http://www.soundjunction.org/default.aspa
http://www.soundsnap.com/
http://www.incompetech.com/m/c/royalty-free
http://freeplaymusic.com/