Links to sites with audio, some of which you can use in your projects:

  • jamendo: It's free, legal and unlimited.
  • NOTE: One can download single tracks by choosing Export playlist to Podcast in the jamendo player, right clicking on the track one wants (on a Mac it should be CTRL Click) and the mp3 file file to one's computer. (You only need to use BitTorent or eMule if you want to download a entire album.)

Not sure if iCompositions is creative commons, but it
is an internet community for aspiring (i.e. not
famous) musicians, searchable by genre. They often
provide MP3 downloads of their own music.

Some/all of the following may be of similar interest: audio (the free sound project.. site may be down)
Here are some possibly useful articles:

Find Podsafe Music For Your Podcast Providers

1 Million Free and Legal Music Tracks

Download Podsafe Music in MP3 format for Podcasts

Podsafe Music Resources!1pXOS7l93k8mqeQ7FlEEmOSQ!907.entry

Set Your Movies to Music