You may have seen this one, but if not: behold the kinetic ingenuity and elegance on display at the BMW museum in Germany.
From the sculpture description:
714 metal spheres, hanging from thin steel wires attached to individually-controlled stepper motors and covering the area of six square meters, animate a seven minute long mechatronic narrative. In the beginning, moving chaotically, then evolving to several competing forms that eventually resolve to the finished object, the kinetic sculpture creates an artistic visualisation of the process of form-finding in different variations.
You can see more photos of the Kinetische Skulptur at http://www.artcom.de web site.
[ Thanks Dave! ]