TinyWM is a ridiculously tiny window manager implemented in nearly as few lines of C as possible, without being obfuscated or entirely useless. It allows you to move, resize, focus (sloppy), and raise windows – that’s it! TinyWM’s main purpose is to serve as a quick example of some window manager programming basics.
Somehow made me change my mind about the complexity of X11. :-) Nick Welch is (or was?) related to Kahakai and Waimea, two other, “big” windowmanagers, too.
He also provides a nicely commented version.
NP: Dan Bern—Black Tornado