Yahoo! Creative Commons Search: "This Yahoo! Search service finds content across the Web that has a Creative Commons license. While most stuff you find on the web has a full copyright, this search helps you find content published by authors who want you to share or reuse it, under certain conditions."
Use the Yahoo!+Creative Commons Search to find open content and copyright free materials for your lesson plans or handouts. This is also a powerful search tool for students (and teachers) looking for open content resources they can use in class projects, research, or reports.
And if you need pictures, be sure to check out the Flickr+Creative Commons Search in Flickr!