.....you might want to check out this resource: MERLOT.
Per the Internet Tourbus newsletter:
MERLOT -- the Multimedia Educational Resource for Learning and Online Teaching -- is a free, peer-reviewed collection of over 13,000 different online learning tools and simulations developed (mostly) by college professors around the world. MERLOT is designed primarily for faculty and students of higher education, but I've discovered that a BUNCH of the stuff in MERLOT's archives will appeal to early teenage students as well. So don't let all the "higher ed" stuff scare you away from what is a WONDERFUL educational resource.
I've been poking around there a little bit, and there's some fascinating stuff available. You might want to start at their awards page to see what they think is the best....