Songs

Maine Music Box http://mainemusicbox.library.umaine.edu/musicbox/index.asp

FreePlay Music http://freeplaymusic.com/

Open Source Audio http://www.archive.org/details/opensource_audio

Gateway to Legal Free Music: Open Source http://www.opensourcemusic.com/

Wikipedia: Songs by Decade http://en.wikipedia.org/wiki/Category:Songs_by_decade