So I picked up an Arduino (www.arduino.cc), some LEDs off ebay, wrote some code, and modded my Satiek joystick.

http://www.youtube.com/watch?v=yRA0MivPk0Q

I think it looks good, but as far as doing that to your PC case.... If its in direct sight when using your computer, I'm sure it would get annoying after like 1.2 minutes. 

Looks like I am going to have to finally get an Arduino.

$35 over at www.adafruit.com. I didn't go with a prototyping shield and just used a giant solderless breadboard from Radio Shack which worked fine. I'm a COMPLETE n00b at electronics like this and -I- was able to get this working It was a big help that the MOO coding I do is very close to this code, so writing the prog wasn't hard at all.

Next I'm gonna mod the leds in my speedpad.. if I can figure out which LEDs it uses and if I can jam them in the case with the existing ones still in place (even though i dont use them)

I have some MEGA plans for arduino + mame cab. .. A marque filled with RGB LED matrices that will display the marque of the game you're playing

Oh most certainly. First, I think I'd need to compile my own version of the MAME prog so I can have it send info to the arduino when a game launches.