http://orbit.medphys.ucl.ac.uk/I've known about this for a while, and flight simulator fans, get ready to rejoice. Orbiter is a pretty realistic space simulator, and it's also really fun. If you have any interest at all in astronomy or space shuttles, and how the whole thing really works, I sugguest a download. It's free, and an open project. There are many add-ons, some of which make the game ever harder, like the Deltaglider IV (my personal favorite). People have made the space shuttles, the Apollo's, and there are even more that I could go into.
It's pretty fun, but it's insanely difficult.
