aewm

aewm - An Exiguous/Exegetic Window Manager 

aewm is a minimal window manager for X11. It is extremely light on features and memory usage, and suitable for slower or embedded systems. It is also intended to provide an example implementation of most of the ICCCM and some of the EWMH, in a simple and clear way, so that you can easily hack on it or appropriate its code for another program. 

It is not, however, an obsessively complete "reference" implementation; features that are distracting or unnecessary have been skipped. The user interface is minimal, and as much of it as possible is implemented in separate clients.