Freesound

http://www.freesound.org/

Freesound has less audio in full song format and more in the way of audio snippets, samples, recordings, bleeps and loops openly licensed for use. This is actually where I ended up finding the audio I needed for my project. There is a wide variety of audio available here from samples of nature and industry, to audio jingles and riffs.

Free Music Archive

http://freemusicarchive.org

The Free Music Archive is described as an archive of public domain and Creative Commons licensed songs managed with a curatorial approach. The bulk of the audio available here is in the form of full songs from artists around the world. The Free Music Archive gives up and coming artists a place to share their bio and link to their home page so that users can learn more about the music they discover.