Physics Education Today has a nifty little site that could be useful for highschool physics classes or younger elementary classes, too, depending on just what scientific principles you wanted to illustrate.
The site uses a number of flash animations to show how electrons move around when a balloon rubs a wall, simulated wave motion, and a half a dozen other cool things. It’s a neat way to bring a physics lab to your students without having a physics lab close at hand. Very handy stuff.