For a lab project, this MIT student created a primitive computer that uses the flow of water, rather than electrons, to power its Boolean circuitry. I suddenly have all kinds of ideas for some steampunk science fiction. Granted, the guy had to use a an acrylic laser cutter to get the consistent friction surfaces needed for reliable water-circuits, but at least he had the good sense to mount all of them to Legos for easy circuit board assembly. Apparently, there is an actual demand for this kind of computational device, particularly in military and spaceflight circles, where core computing systems need to resist extreme radiation environments (like say, the Van Allen Belt or Ground Zero). Check out the pics!