Check out the Flight Sim Toolkit Site and find close to 20 FREE flight simulators ready to download. Another cool Flight Simulator site is Comox Valley Flight Simulator Stopover - wings.ark.com.
If you'd like to tune up your computer so that it runs the simulators the very best, then you'll want to visit Flt Sim Tuneup Page. For info on the U.S. Navy Fighters program, check out the U.S. Navy Fighters (Marine Fighters) Homepage which is in the Netherlands!
Many cool flight simulator demos and patches can be found at the Electronic Arts page.
The very best input hardware can be found at Flight-Link.
Now Microsoft has a Flight Simulator, FlightSim98. But for the finest in simulated flight, I suggest you try ProPilot by Sierra.