as a part of my learning relativity, I've written a fully dynamic special relativity simulator. It simulates relativistic motion of bodies (similar to ODE and Bullet physics engine, but rather simpler in some aspects and using relativistic physics); time dilation, length contraction, accelerations etc. It can show the world as-is for the current observer or as-seen. There are Linux builds and sources available. I'd appreciate any feedback, even if you don't know about relativity, I'd be glad to hear how it runs/or not on your Linux box. Should work with ati r600g open source drivers and fglrx, not sure about the others. Downloads at http://thelarge.org