I bought the Digital Juice royalty free music volumes BackTraxx. What I liked about their collection, besides being decent music, is that their license is very broad with very few limitation.
Here is a link to their site: http://www.digitaljuice.com/
Here is a link to the BackTraxx collection: http://www.digitaljuice.com/products/product_volumes.asp?cid=1&pvid=1
Here is a link to the license: http://www.digitaljuice.com/products/product_docs.asp?docid=54
Item one in the license is a recent addition but basically restricts using the music as the primary purpose of the activity.
Royalty free music comes with a license which you need to read thoroughly because they sometimes provide some very restricted uses.
