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...

Homepage:
http://ctwm.org/
