Indaba Music launches audio clips library with over 8,000 CC-licensed samples and loops: http://www.indabamusic.com/clips
The clips database is searchable by musical key, tempo, tonality, time signature, license type and source.
I use a few pages to find music for my podcasts:
Jamendo – of course. You can simply chose a license and search with that.
The Internet Archive
Musopen – Classical music, all public domain though.
ccMixter – Samples and music, search mainly on title
opsound – Gift economy
Royalty Free Music – All CC-By licenses
SoundClick – Genre-dropdown ….
Simuze – Dutch [...]