I've been fascinated by stereolithography since I heard about it years ago. Originally it involved lasers and a polymer bath. The 3-D object literally rose out of the liquid polymer as it was being cured by the laser.
While not exactly the same process this company ShapeWays in the Netherlands looks extremely interesting. Essentially, they can bring your 3-D models to life in a variety of materials from stainless steel to glass to metal. I'm thinking this would be a great thing to use to teach kids or adults to use the 3-D modeling software packages.
In the past prototyping was an expensive process and was a barrier to entry. Now someone at home with an idea for a widget has the capability to get it done cheaply and professionally.
Video showing huge stereolithography machine making a car bumper prototype