For those of you sick of using the Soundtrack Pro loops.
Royalty-Free Music: Typically refers to music that you can use in perpetuity once you’ve paid a single license fee.
http://www.audionetworkplc.com (Rate Card > Music Blanket License)
http://incompetech.com/m/c/royalty-free/ (FAQ: Is this music free to use?)
(License) http://creativecommons.org/licenses/by/3.0/us/legalcodearchive.org (FAQs > Rights)
http://www.digitaljuice.com/support/ (BackTraxx 2)
If you're looking for classical music, check out https://musopen.org/