Kinetic Sculptor Bradley Litwin, who's been making machines since he was a child, now makes what he calls "Mechanicards." They're moving pieces of artwork no bigger than a CD case. In fact, they're meant to be shipped in CD case boxes.
All of Litwin's sculptures move in some way — but that's about all they have in common. As he says: "There's not much I won't give consideration to if not try and actually make."