An excellent curriculum/resource page for teaching students about copyright. Covers history of copyright; quizzes to see what students know; the concept of fair us; issues with remixing, mashups, and file-sharing. Contains links to further resources.
On this website, Wesley Fryer gives some great definitions of copyright rules, including a mnemonic device to use with students to help them remember the basic principles of sharing media ("Harry Potter Can Fly"). There are also other good links and a video all on the theme of fair use and copyright.