http://www.neok12.com/ NeoK12 “Educational Videos, Lessons and Games for K-12 School Kids” from their website. This site is iWatchDog ICCS certified and offers a huge variety of topics ranging from History to Science.
http://www.toporopa.eu/en/index.html Toporopa. This website is best used for review or tests for European geography. It is an excellent quizzing website.
http://phys.org/ Everything science. And I mean real science. Registration is free, you can sign up for different topics to drop into your email address. This is real science news, so use it for yourself or older high schoolers.