These are sites where you can find music to legally use in your videos.

Please read the terms. Some sites require that you give only give attribution while others sites expect you to pay a license fee. 

***please add more sites with explanation***

1. http://pumpaudio.com/ :  You pay per license.
2. http://locarecords.com
3. http://OpSound.org: All their music is under CC-Attribution-ShareAlike
4. http://promonet.iodalliance.com
5. http://magnatune.com

6. http://music.podshow.com
7. http://www.ccmixter.org/: all of it has a cc: by license
8. http://www.feltonjamhouse.com  Feel free to use any music found here.  I am a videoblogger and I made this music and host the site.  Go ahead download and use! 
9. http://www.archive.org/details/audio
10. http://www.dpop.es/. Spanish pop published under creative commons.
11. http://www.jamendo.com/en/: seems very open and is all about sharing.