Written in Python, wypy may be the world's smallest wiki at just 23 lines of code. I wrote it months ago, but have only just released it. Also: the smallest wiki contest, and the wypy source code. Released under GPL 2: share and enjoy!
And yes, I know that months ago I said I'd update miscoranda a lot more often. But I've been a) busy writing the world's smallest wiki, and b) busy procrastinating from writing the necessary miscoranda interface code. Busy times. But hey, I posted this, so that's a start.