Karabiner

Karabiner, previously called KeyRemap4MacBook, is a very powerful keyboard remapper for Mac OS X. In addition to simple key remapping, it has special remapping modes like Emacs-mode, SandS-mode (Space and Shift).

Free Open Source Mac OS X

ControllerMate

ControllerMate is a controller programming tool that allows you to customize the behavior of your HID devices — keyboards, keypads, mice, trackballs, joysticks, gamepads, throttles, among others.

Commercial Mac OS X

Seil

PCKeyboardHack can change caps lock key behavior. For example, changing caps lock key to delete Key. PCKeyboardHack can activate International Keys on Non-Apple keyboard.

Free Open Source Mac OS X