Joystick Mapper - Use Gamepads in any Mac App or Game
Joystick Mapper is an application for Mac OS X that lets you map keyboard keys, mouse axes, mouse buttons and mouse wheel to any joystick or gamepad button/axis/hat.
In other words: This App will let you play any game or use any app with any joystick or gamepad, even the ones that are not compatible with joysticks.
Youtube link | Pop Up
website with help and more info:
(Check also the Joystick Show : a gamepad tester app)