The winners of StarshipModeler.com's "Wrecks" challenge are a mixed bag, with some absolutely incredible destroyed sci-fi models, both kit-built & free modeled, and dioramas. And then others that are less impressive.
Art on a napkin: Before ketchup art, before Esquire Napkin Fiction, there was the Mama's Royal Café (checks and credit cards are cheerfully not accepted) napkin decorating contest. Enter now, (or, maybe don't. I don't want anyone to hurt my chances here!)
Rube Goldberg, former mining engineer, Godfather to Mad Magazine’s “Snappy Answers to Stupid Questions,” cartoonist for Boob McNutt and Mike & Ike (they look alike), is best known for the now eponymous machines he started cartooning back in 1914 such as: how to not forget to mail a letter. Or the reminder to take out the garbage. Or the local government efficiency machine. Or the oversleeping cure. Or the German webserver wakeup device (it’s got sound). There are amateurs making ‘Rube Goldberg machines,’ but there are also serious contests, sponsored by serious engineers. (There are even do it yourself plans - y’know, for kids). Goldberg’s influence can be seen in a variety of media, but by the time he turned 80 he’d tired of cartooning and decided to begin sculpting. Needless to say he excelled and of course, influenced humorous kinetic sculpture.
CG Challenges - the largest online art contests of their kind, where artists are challenged to create outstanding artworks based upon set themes, while working under restrictions. For CG students, an additional bonus is the view of the creation process.
If you're the type who gets creative when you drink a lot, the folks at Canstruction have a few ideas about what you can do with the discarded empties. Here's a slide show of some good examples, and here are the winners of their contests in 2002 & 2003 respectively.