GNOME 2.2 officially incorporates the Metacity window manager, a fully integrated window manager that uses GTK+ for UI elements, communicates tightly with the panel and other desktop elements, and is configured straight from the GNOME preferences dialogs. At the same time, all interaction between the window manager and the desktop is done via documented standards (see the section called "Standards Compliance"), so you can substitute the window manager of your choice from a long list of available options: Sawfish, fvwm2, icewm, Waimea, Openbox, are just some of them.