A particularily light window manager is FLWM (Fast and Light WM) which is included with Debian as of 2.2/Potato. Check it out at flwm.sourceforge.net. I currently have two desktops running and the memory footprint is 750 kb. I am a BIG fan of FLWM and here are a couple of reasons:
o lightweight and uses very few colors (duh) o window title bars are on the left side of the window (not the top) which means you can use EVERY PIXEL in the verticle direction o The window decorations include maximize-verticle maximize-horizontal buttons (as opposed CTL-SHFT-Click-Maximize or something) o Menus and submenus of applications are very easy to setup and do not require root privliges. o Supports multiple desktops (Ctl-Tab between them or via mouse/popup menu) o Many keyboard shortcuts o The source is very short so it's easy to tweek. (it's based on the FLTK -- Fast and Light Tool kit) o of course, it's GPLed
