Commercial music

The majority of music released under a CC license uses one of the licenses that prohbit commercial use (for purposes of verbatim distribution this includes all of the "sampling" licenses, even ones that allow commercial derivative use). There is as yet no web-scale audio-specific CC search, so here are some pointers to finding music that allows commercial use at some of the CC Content Curators.

ccMixter

http://ccmixter.org/media/tags/attribution -- all tracks under a plain BY license. Add genre and other filters to the list by clicking '+' next to the desired filter on the right.

http://ccmixter.org/media/playlist/browse/44 is a playlist of 100 tacks under a plain BY license chosen by the CC Creative Director in February, 20007.

Jamendo

Browse Jamendo by license at http://jamendo.com/creativecommons/

The same page has a search box that allows you to stipulate that you only want to find music that permits commercial use.

Others

Many other sites host some music permitting commercial use, http://archive.org and http://www.dogmazic.net in particular. Add instructions here for finding only commerce-allowed music at these sites.