I've also put together an Xbox 360 pad mod so I could use my old Atari joysticks to play Pac Man Championship Edition. It works perfectly and makes a lot of 360 2D games WAY more fun. (Hey microsoft, your D-pad sucks!)
Also updated or added the following:
PC Engine Controller Schematic
Megadrive/Genesis 3-button Controller Schematic
As usual, most of the action is on The Forum.