CTWM is an extension to twm, that support multiple virtual screens,
and a lot of other goodies.

    You can use and manage up to  32 virtual screens called workspaces.
You swap  from one workspace to another by  clicking on a button  in an
optional panel of buttons (the workspace manager) or by invoking a function.

    You can custom  each workspace by choosing  different colors, names
and pixmaps for the buttons and background root windows.

    Main features are :

        - Optional 3D window titles and border (ala Motif).
        - Shaped, colored icons.
        - Multiple icons for clients based on the icon name.
        - Windows can belong to several workspaces.
        - A map of your workspaces to move quickly windows between
          different workspaces.
        - Animations : icons, root backgrounds and buttons can be animated.
        - Pinnable and sticky menus.
        - etc...