This site monitors the use of copyright claims to silence free speech. There's a generator for responding to complaints that you're violating copyright.
I view (and use) this resource much like I do YouTube videos. It contains a massive store of diverse resources to use to explain or enhance lessons. I really utilize, and find success in capturing the kids' attention, the primary source resources history.com has--videos and pictures of old speeches and battles, original copies of documents. Doing so helps the kids relate the information, which may seem abstract to them, to actual, real-world things and occurrences!