I found an NES controller in a box today and hooked it up to the Arduino. I don't have my NES anymore, but it could be a pretty cool, easy to use set up controller for something else.
Do you like old-school games? If you do, you should hook your controller up to a computer and download a NES-emulator. 
http://www.i-hacked.com/content/view/143/101/ Really simple stuff! I have a laptop hooked up to my tv, with a SNES-controller attached, running zsnesw. Countless hours of fun for Nintendo fans. =D
The code isn't on your original site anymore. I've got a tutorial with the code for reading the controller:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1254964306/0#0
It's for a 1980's original NES controller.
arduino tetris nes controlled anyone???