I use a Mac Mini as a media center computer. While I generally like Front Row, and have a few custom (unsupported) plugins, sometimes you really just want something one button away. I’m already using a universal remote, but the Mini’s built-in IR receiver can only detect the signals for the 6 buttons on the Apple remote.
As a quick-and-dirty solution, I wrote this sketch for the Arduino, using a generic IR remote receiver. When reset, the Arduino starts listening for an IR remote command. It remembers the timing of the pulses, then listens for a similar set of pulses and signals over the serial port. I wrote a few lines of Python to listen to the serial port and do something interesting.
Now I can eject a DVD without messing with any menus. I’ll probably need a more complete solution some day, but for now, I’m set.