I've read through parts of Ratpoison, aewm, Awesome, XMonad, Blackbox, and other WMs over the years. Short source like this can be very helpful in other ways, though - seeing a very simple Scheme interpreter or minimal webserver in Python (or whatever) can make previously "hard" things more approachable. The "hey, you can do this too" energy or big picture insight from overly-simple-but-still-functional code can be just as helpful as deep references sometimes.

As WMs go, I've had an itch for a while to write a skeleton WM in C with hooks to script it in Lua. dwm continues to work just well enough for me, though, and I've already got too many projects. One of these days... (And no, Awesome and XMonad don't do it for me.)

Also, for anybody doing any kind of exploratory X WM programming, it's incredibly helpful to use a nested X server such as Xnest (http://www.xfree86.org/4.0/Xnest.1.html) for debugging. Something like this should work:

   #!/bin/sh
   # -ac allows connections
   Xnest -ac :1 &

Then you can say e.g. "xeyes -display :1" to run things inside it.