Cross-platform, open source flight sim

Flight sims used to be a popular sub-genre of video gaming. Still are in some parts. And while there are still plenty of choices, I think it's pretty cool there are some spiffy open-source projects carrying the torch. Enter FlightGear

Fly a bunch of Cessnas, a few military aircraft, the space shuttle, or a UFO among other aircraft. And you can leisurely fly around a whopping 20,000 airports— the entire world on 3 DVD's. The graphics are good if not inspiring, but a looked decent nonetheless on my paltry 32 MB VRAM ATI card... Joystick control is a bit spotty, but the documentation gives you complete instructions on getting your input devices to work.

You can't beat the price at free, and the app runs on Mac, PC, Linux, FreeBSD, IRIX, and Solaris. What's exciting about this (and most open-source projects) is the ability to tweak and experiment. Most internal game settings and even controls are manipulated through XML files. There are built in hooks for networking. So you could remotely control the flight engine through a networked script. Why? I'll let you figure that one out.