CrashCourse Six awesome courses in one awesome channel: John Green teaches you US History and Hank Green teaches you Chemistry. Check out the playlists for past courses in World History, Biology, Literature, and Ecology.
The Ketchup Experiment! Kid friendly site with lots of neat experiments! It has one that makes a rocket out of a film canister, which would be good for an grade space unit, but it has to many kid friendly expiriments. Great site for any science teacher.