We've already ascertained that 3D printers are cool. But when connected to an iPad, running the Beautiful Modeler app? Consider our collective minds blown. You can mould digital clay into whatever you want, then print it with a 3D printer.
You'll need a 3D printer, obviously - MakerBot's Thing-O-Matic is the cheapest, at $US1225.
It's probably the easiest way to design 3D objects, without mucking around on CAD or other design programs. Actually using your fingertips to bend the lump of clay within the iPad app, turning it into a little object to print out - well, it sounds like a dream come true. Imagine your mum making Christmas tree ornaments this way, or being able to conjure up a little doohicky for sliding under a short table leg, within minutes?
Never have I wanted a 3D printer so much before.
The source code is available to grab from the Interactive Fabrication site now, and cleverly the program actually hooks up your laptop at the same time, so you can see your object's progress there, and model it on the iPad. [Interactive Fabrication via CreativeApplications via FastCo]