There are many ways to find Creative Commons licensed work! A good starting point is the Creative Commons web site. They offer a search interface that gives you links to nearly a dozen search tools to find images, clipart, video, music, and other media.
Browse by genre (hip-hop, country, classical, etc) or search by keyword. "The Free Music Archive is an interactive library of high-quality, legal audio downloads directed by WFMU, the most renowned freeform radio station in America."