The guys over at WoodGears.ca have outdone themselves again with this awesome binary marble adding machine.  It is a rudimentary example of how binary works.,  but makes for a killer display with all the marbles rolling down, setting other levers and causing chain reaction, resulting in the correct answer .  Give geeks free time and expect something like this as result..

In a way, I want the blueprint to make this just so I can make something for my son for his birthday.  but I can't see the blueprint there yet.