The Fear of Physics Web site contains more than twenty interactive physics related activities. Everything from things that spin, sound, atoms, collisions, and the Doppler effect are included. The Speed and Acceleration link teaches about movement by allowing users to choose two vehicles and change their position, speed, and acceleration. After pressing the GO button, the program runs, and students get to see how the chosen variables affect the vehicles' movements. A great collection of online learn-by-doing experiments.