Regular iMac, just with an extra 128 MB or RAM in there.
NOTE: There is no keyboard (it broke) and I can't find the hockey-puck mouse (Put it in a drawer a while ago when I replaced it with an optical).
If you are buying new the lack of input devices makes this pretty inconvenient, I admit, but the added memory almost makes up the difference in price.
asking $500 to start. Definitely negotiable.
PS. If you're in the New York City area, some kind of drop-off or pick-up can be arranged, and you can avoid shipping.