I picked up a Keyspan Digital Media Remote today. As long as you install the beta driver (scroll down), it works flawlessly (the volume control doesn't work in the production drivers on recent versions of OS X).
With this, I can now remotely control the iMac that acts as both the main music library and occasional DVD player. Out of the box, it is quite useful; track forward/back, volume, mute, play, pause, stop and a handful of other keys I can't remember.
The "key editor" will let me assign AppleScript scripts to the buttons, as well. So, I'm going to make the directional buttons set the rating on the song and the select button effectively do a Do not ever play the currently playing song again. Not ever. It sucks. Make it go away! Play the Next Song!!!
Cool gadget for less than $40.