What is WatchKnow?
Imagine hundreds of thousands of great short videos,
and other media, explaining every topic taught to school kids. Imagine them
rated and sorted into a giant Directory, making them simple to find.
WatchKnow--as in, "You watch, you know"--is a non-profit online community
devoted to this goal.
This is the same stuff you get on many of the paid subscription websites. You do need to sign up to use this site. Also, it appears to be in development with new resources being added regularly. As of right now, it is a little light in the upper ages and grades.
Most Recently Added resources found at this link