Archive.org is a great source for free audio.
They have a huge inventory of public domain music, as well as music licensed under creative commons or other "copyleft" means. I have gotten audio files for backing tracks for podcasts. I have used audio books for Uncle Tom's Cabin, The Wizard of Oz, and Main Street for my history classes. And, I have used some of thier speaches for my history classes.
Submitted by Rick Burkett, Carterville, Illinois