This let's you do a variety of experiments with a frictionless "puck table." You can adjust the intial velocity and direction of the pucks, and make a variety of selections including magnetic pucks, a tilted table, inelastic collision (including rotational motion), and viewing of the center of mass.
The spark generator gives you a snapshot of where things are at given time intervals. I will certainly get some real documentation up for this one as soon as I can, since this experiment can be used to simulate a tremendously large variety of physics. By looking at the spark tracks you can determine the velocity and acceleration of the pucks under a variety of conditions.