Making the blog rounds is the plans for the worlds first randomly assembled supercomputer. Randomly assembled meaning in this case that it will be made up of just the machines of the people who show up.
This presents interesting ideas for a lot of other venues: Why don't some airport sponsor a flash mob computing event: Provide the airport WiFi link as the networking infrastructure for free. Or how about The Cinnamon Decaf Soymilk Extra Grande Moccachino Computer - made of Starbucks patron computers all over the world. Donate the time to SETI and give away free muffins with every detected radio spike.