The music on ccMixter.org is generally licensed to be used in any arena, not just the ccMixter site or a specific contest.
Filmmakers can adapt the music for their films/videos by editing the length or adding voice over.
Mixkit is a website for royalty-free music from Envato. Limited tracks can be downloaded free and a subscription is required for unlimited downloads.
The Free Music Archive (FMA) is an online repository of royalty-free music, established in 2009.
On Audionautix, all music is composed and produced by the same musician – Jason Shaw, who is based in Pennsylvania.