This is a water-cooled alternative to the fan cooler on the RepRapPro Huxley and Mendel: http://reprappro.com
The device is a drilled and tapped brass block. When it's been machined, blank the small hole ends by soldering in a few mm of brazing rod, and solder in a couple of 4mm copper tubes. Connect it up with soft 3mm i.d. silicone tube to a small gear pump or similar. The flow rate needed to keep it cool is not great.