You know what happens when you use music by a famous artist in your videos, even if it's a little snippet: Your video eventually ends up being taken down, and you could possibly be in trouble. Some time ago, Youtube introduced the "Audio Swap" tool to help alleviate this problem, but it's not perfect.
So after browsing Wikipedia on the subject, I found about the FREE!MUSIC project:
http://en.wikipedia.org/wiki/FREE!MUSIC
You can use any track from their library in any type of project, even commercial ones. What's the catch?
Sounds fair to me. Here's the page from which I extracted the quote:with one condition - the copyright information and author's contacts must be retained
http://freemusic.org.ru/en/node/41
Here's the index by music styles:
http://freemusic-project.ru/en/indexpage/flexinode-1