Back from Christmas holiday’s, I found a nice one on Hack-a-Day. A short article on Nudel (nickname, I hope;), who documents a way to print worlds and objects from Minecraft with a 3D printer.
I guess there are more people playing with this now, but this is the first completed and well documented method I found. Be aware that in order to get the color prints, you should probably send your models of to a service like sculpteo or shapeways.
The lack of resolution on the RepRap and other home 3D printers is an edge here though which gives the finalised models a great Minecraft-y look.