"For the last couple of years Vimeo has offered free music to download and re-use in your video projects. Now YouTube is offering the same thing through the YouTube Audio Library. This library is slightly different than the free music available when you use the YouTube slideshow creation tool. The music in the YouTube Audio Library is music that you can download to use in projects online and offline. You can search the library of music according to genre, mood, instrument, or duration. You can listen to the tracks before downloading them as MP3 files."
Via John Evans