If you're like me, you looked at this picture and the name "Three-Pendulum Rotary Harmonograph" and felt confused and a little bit threatened. But fear not! Turns out it's one of those fun spirograph-like things you see at science museums.
This one uses three pendulums, which creates some pretty complex and cool-looking patterns, even better than the clear plastic spirograph I used in third grade. The project isn't even all that hard: Looks like it takes a bit of careful balancing, but the actual construction is pretty standard woodshop kind of stuff. Pretty cool! [Karl Sims via MAKE]