Ingenious YouTube user and Minecraft Designer ItsJustJumby has created a kind of virtual 3D printer in the world of Minecraft.
Minecraft, if you're not aware, is a simple to use 3D virtual environment where people can design and build, well, anything!
Even though the "printed" output appears quite simplistic to real 3D printer aficionados, the virtual 3D printer operates by a rather complex collection of thousands of Minecraft components that act in a digital-like manner to produce the required printing effect. It's pretty slow, but it does work, and demonstrates how you can make a programmable environment do almost anything. Check out the video to see how it works:
Even better, you can download the virtual printer and check it out yourself.