Rube Goldberg machines are fun, as anyone who has seen The Goonies will tell you. Physical machines, such as the meticulous, elegant design built for the award-winning Honda ad “Cog” (which required 606 takes to get right), cost millions of dollars and take months of work to film.
A recent trend on the web is the building of virtual Rube Goldberg machines, using existing video game engines to supply the components and physics, and essentially developing their own emergent gameplay. Half Life 2, with its included Havok physics, has an entire community working on building various exceedingly complicated contraptions that do very little, by tying together various blocks, pulleys and the ubiquitous exploding barrel. For my money, the finest examples of the art have come from the venerable Super Mario World.