Someone just sent me the link to this site (Thanks Christopher!) and I have to say I`m impressed. It`s a new product, which is a pretty neat spin on a normally common idea.
The Retro Adapter is a device which lets you connect all types of old game controllers via USB.
By default, you can plug in Atari / Commodore style joysticks, Sega Master System / System III, and Sega Megadrive / Genesis (3 and 6 button) pads in to the 9 pin connector. Neo Geo joysticks / pads can be plugged directly in to the 15 pin connector.
For other systems all you need is the right connector, or you can modify the controller itself while still retaining compatibility with the original system.
Once plugged in, the Retro Adapter works just like any normal USB gamepad or joystick. No need for drivers or anything like that. It will work with any game or emulator, and is compatible with Windows, Mac OS X, Linux and the Playstation 3.
It`s even more unique because the Retro Adapter is also open source hardware and you can even download the complete schematics and source code to make your own.
You can also buy ready made adapters instead of making them yourself.
Check out the site here.