For the Overload 2012 launcher game I hacked together support for multiple simultaneous Joysticks in Monkey (The first C programming I had done in a decade!). I did a bit more work on it today and turned it into an enhanced Joystick support library. It can handle:

• 16 Joysticks simultaneously
• 128 buttons per Joystick
• 8 axes per Joystick
• POV Joystick hat support (Necessary for the XBox 360 controller's DPad)
• GLFW on Windows only at this stage. Mac support shouldn't be too hard to implement, XNA is another possibility.

Source has been bundled into the Earok's Monkey Demos pack.