Those are cool...engineering students often build them. What I like about this one is the number of 'homemade' items in the mix.
One of the best I saw recorded, one that uses a lot of chemical reactions as well as simple mechanical processes was shown on the TV show "Alive From Off Center." The particular clip is titled
Der Lauf der Dinge.
Also, in deference to Scott's invention thread...note how many variations on the basic wheel are used in that set-up.