[astralpancakes] wireless arcade stick project looks like a great place to start if you want a simple project. Well constructed arcade sticks can cost $100+, but with all the MAME cabinet builders, the parts have become easy to acquire. The stick has a rigid wooden case with a metal faceplate. All of the component connections are soldered to the pads of a Logitech wireless controller. [astralpancakes] built this specifically to play Street Fighter III: 3rd Strike.
The Universal PCB project lets you make any controller (specifically arcade sticks) console agnostic. A PIC microcontroller is used to translate between the button presses and the signals for the specific console you’re connected to. It uses a DB15 for the external plug. The PIC knows which console you’re plugged into based on which pins are high or low in your console specific adapter cable. The board includes a piggyback plug so you can plug in an Xbox360 controller board (like the one above) since the console requires authentication. The PIC’s firmware is conveniently upgradeable over the USB cable.