The wired version of the xbox 360 controller can also be used as a PC game 
controller.  I tried this out after getting frustrated trying to drive in some racing demos
I downloaded.  The keyboard controls for those demos were awful, it was very hard
to even drive straight.  After installing the 360 controller, all was great.  I could configure
what buttons did what, and could use the analog stick to steer.  Not all games support
a gamepad controller, so I can't use it for all games.  But driving games, halo pc, sports
games, and platformers are now much more enjoyable for me.

If anyone else is interested in a pc gamepad that rocks, post here and I will give you more specific details on which version to buy and installation info.