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 [...]