I am writing this from crystal (fvwm based) it is a light an nice window manager.
The package is now in Edgy (universe), all you need is to enable universe repository and execute:
sudo apt-get install fvwm-crystal
Then logout and change the session when you login again. If you do not have Edgy, or want to try a newer version, execute the following in a terminal (you may want to change the version number to the latest one).
To findo out more:
sudo apt-get install fvwm python imagemagick rox-filer\
xscreensaver trayer gksu aterm habak mpd mpc
tar xvzf fvwm-crystal-3.0.4.tar.gz
sudo make install
sudo cp addons/fvwm-crystal.desktop /usr/share/xsessions/