With 2400 LEGO bricks and a lot of patience, [Will Gorman] built a LEGO 3D printer. It’s similar to a RepRap or a Makerbot, but instead of extruding plastic, it uses pre-extruded building blocks (aka LEGO bricks). The grey wall extending far above the unit itself is a feed magazine which holds the raw material. A Java application takes an MLCad file and translates it into building instructions for the printer. Those instructions are then sent to the device via USB. See it happen after the break.
Now this just needs to be combined with the LEGO sorting machine for an inexhaustible supply of bricks.