PBS
Pbs Learning Media: Galileo: His Experiments
This interactive activity from the NOVA Web site samples Galileo's experiments with falling objects, projectiles, inclined planes, and pendulums.
American Museum of Natural History
American Museum of Natural History: O Logy: Train of Thought
Try out your ability to think like Einstein by working through two thought experiments that help explain how satellites stay in orbit and how the speed of light affects the universe.