One of the great advantages of using a free license for a work is that you can re-use a growing body of free-licensed source material to help you do it. But it can seem a little daunting to find the material that you both want and can legally use. Here's a little bit of my strategy, a few tips, and some sources, including Jamendo, which I found to be the most useful for finding music. I also touch upon some useful free software tools for listening and sorting tracks.