Since a few people expressed surprise at the 3D printing technology Rachel described in tonight's opening segment, I thought it might be worth a wee hour post on how a 3D printer works. Here's the somewhat famous Bre Pettis of MakerBot at last year's CES explaining how it works. Unlike the metal CNC machines you may have seen on those bike builder chopper shows on TV that cut away pieces from a solid block, the 3D printer is additive. So you enter the 3D design you want, the software breaks that into thin layers and then traces each layer with melted plastic, adding more thickness until your object is formed. The plastic comes in a spool, looking like a thick wire that feeds right into the printing head.
It used to be that the layers were relatively thick and you could see them in the final product so you'd have to finish them with a bit of sanding. But it looks like the new MakerBot Replicator is bragging about 100 micron layers that don't even need retouching.
You can make your own design or you can go to a catalog of pre-made designs. For MakerBot, that catalog is called the Thingiverse.
I keep referring to MakerBot because I think they're the best known maker of 3D printers, but at roughly $2000, they're definitely not the cheapest. RepRap is an open source 3D printer project. The idea is that once you have one, you can print out the parts to make another one. So as far as I can tell, you don't buy a RepRap printer from RepRap, you buy one (or just parts of one) from a third party. Poking around, the cheapest assembled one I found was $800.