ccMixter

From site:  ccMixter is a community music site featuring remixes licensed under Creative Commons where you can listen to, sample, mash-up, or interact with music in whatever way you want.

Remixers If you’re into sampling, remixing and mash-ups grab the sample packs and a cappellas for download and you can upload your version back into ccMixter, for others to enjoy and re-sample. All legal.

Video makers, podcasters and music lovers, if you’re into music, browse this site to hear some of the great remixes people have built from sampling music on this site, all licensed for use under Creative Commons license.