Lizzie (one of our awesome librarians) has put together a guide to free stuff out on the web. She has focused on quality sites that might be useful for students doing research, putting together presentations, and working on course-related projects.’
You can find this guide here: Free eBooks, Images, Music, and Videos.
Many of these sites include limits on how you can use them. Thus, this guide also includes links to Creative Commons info, which will help offer guidance on usage.