I recently did something somewhat physics related, implementing Kepler's laws of planetary motion in JS to produce a 3d simulation of the solar system: http://www.asterank.com/3d/ ...I plan to generalize it into an open source educational tool that allows people to build arbitrary space simulations on top of its physics engine.

Another interesting JS physics experiment that I found while looking into this stuff is this n-body gravity simulator: http://www.spacegoo.com/solar_system/