http://www.sealiecomputing.com/retrozone/retropad.html

USB NES Controller - The only difference from the classic Nintendo controller is the long 5 foot USB cable. No modifications are made to the internal plastics of the controller, so the RetroPad is just as sturdy as the original. It can easily survive the throw across the room you know is coming. Even small details like the black cable make the RetroPad look and feel like the best rectangular controller ever.

Standard USB HID Gamepad
Works with MacOS9/MacOSX/WinXP/Win2K/*nix)
No drivers needed
No adapter boxes
No complex or ugly wiring
Only original controllers for classic feel
Black USB cable looks like the original