KSP is a game where the player creates and manages his own space program.
Build spacecraft, fly them, and try to help the Kerbals to fulfill their ultimate mission of conquering space.
Indie title, still in development and the software is currently free. Essentially a rocket physics simulator - build a rocket with a variety of modules (solid fuel boosters, liquid fuel tanks and gimballed nozzles, attitude thrusters, etc) and see if you can get it into orbit... or even the "Mun" (good luck with that).
I've managed to waste a few hours now building rockets with varying degrees of success - only managed to achieve orbit once so far, and have managed numerous catastrophic launch failures.
There's a user wiki here: http://kerbalspaceprogram.com/wiki/inde ... =Main_Page
Great little time waster.