What if a bunch of geeks, not nessesarily coders, get together and jam on a topic, piece of code. Time? Depend on the topic - you wouldn't write the linux kernel in 15 minutes. You could compose a beautiful 5 line code poem in a few minutes though.

Something along the lines of OpenSpace, BarCamp, FooCamp, LUG meetups, tag tuesdays, fill your own.