I'm currently using Ubuntu 11.04 using the "Ubuntu Classic" session at login (Gnome 2). I recently tried xmonad as the window manager for the Gnome session, and I like it when my laptop is plugged to a big monitor; I used the method outlined here to get xmonad as the window manager and keep everything else Gnome. When I don't have my laptop plugged in to another monitor, I prefer metacity due to the limitations on screen real estate.
Is it possible to create two Ubuntu Classic sessions, each one using a different window manager? If so, how? I am aware there is an xmonad session in itself, but this isn't what I want as I would like all the features from gnome to be kept.
Alternatively, is it possible to change the window manager inside a session without logging out? This would be even MORE useful.