Lifehacker picks six ways to find reusable media:

You need an image for that brochure you’re designing, and you need it now. Put your hands in the air and step away from the cheesy clipart, mister. Thanks to organizations like Creative Commons, licenses like the GNU Free Documentation License, and the public domain, there are tons of photos, songs, movies and documents freely available for you to download and republish without fear of the copyright police.

CC’s search interface is resource #1.