Scourge of War Boards

Here is the webpage for downloading the Orbiter Space Simulator. Also make sure that you visit the other links as well since they offer up free downloads that are simply a must to have for the Orbiter Simulator.

Of course, it's free of charge. Also note this has a steep learning curve...

Orbiter Simulator Website: http://orbit.medphys.ucl.ac.uk/index.html

Thank you LMUStats for reminding me of this Simulator.