Long time readers here should know that I have a bit of a fascination with strange, retro computing devices. While I haven't done anything significant in this area myself, I love to see them, and at yesterday's MakerFaire, I saw Simon's Relay Calculating Engine. I'll let Simon explain it to you:
My own impressions: it's brilliant. In the front it has a real presence. The cabinetry is beautiful. The interface is crazy in its retro feel: a rotary dial and metal pushbuttons, with Nixie tubes for output. There is even an awesome mechanical cam in the front that generates the two-phase clock signal. And the back is equally impressive, a maze of wiring connecting dozens of relays. Very cool.