Crazy dreams

3D printer kit hasn't even arrived yet, and I've already thought about, and had dreams about building a computer controlled X-Y router platform. Really, for the accuracy you'd need to print signs (1mm or maybe a little better), you could slap something together in a weekend out of drawer slides. And if it could hold a router, or a felt tip pen, or a razor stylus, or anything else, it could do a lot of stuff.
The software would be the hard part but I bet there's already an OSS project that's done that bit.
This started as a G+ hangout discussion, but I'm afraid it could be a future project.
( G+ comments below the cut )