Today I discovered the non-profit organization that makes Wikipedia possible. I didn't realize they have other "products" including Wiktionary, Wikiquote, and even Wikinews where you can submit or read news articles from all around the globe.
The division I am most excited about is Wikimedia Commons. Here you can find images, sounds, and video free to use. Yippee!!! This will provide a lot of content for a website I'm working on.
One interesting video that I can see generating a lot of math problems is shows a mechanical clock created in 1509 in Nuremberg. By today's standards, it's no Timex, but it is still very cool.