Comment Turn it into a MAME machine! (Score 1) 620
Build or find an arcade cabinet and use one of the computers as a MAME emulator. You can use an old monitor or TV for a bigger display, and you can even build an arcade-style joystick by taking apart a cheap PS2 controller and hooking up arcade buttons to it. There are lots of places that sell the buttons as well as plenty of tutorials on how to build joystick controllers. Here's a couple sites:
http://www.xgaming.com/arcade_buttons.shtml
http://wrongcrowd.com/arcade/parts.shtml