Royalty free music sites
http://incompetech.com/
Suggested by Erika Rossi.
http://mobygratis.com/
Marco Righetto found this nice initiative supported by the artist Moby—mobygratis. It’s a web site in which you need to register to download music for free, as long as the music is used for non-commercial purposes (e.g. a thesis project). Of course there is a lot of creative commons music, but these tracks are usually “better” than the average you find.
http://ccmixter.org/
CHI video submissions recommended.