Been Playing Kerbal Space Program

Interesting game as hell. After initial false launches and falling back onto Earth, I figured out the proper launch maneuvers and finally put barely a capsule into orbit (after spending too much fuel). Subsequent flights I got better and got more efficient.

It's an awesome simulation - check it out. I would not call it realistic simulator but I did learn a lot about space flight trajectories, orbiting manuevers, etc from it. You can actually get to the "Mun" and other planets in that solar system, however. I never actually got there, yet.

Download the demo version: http://www.kerbalspaceprogram.com