With olvwm (an older window manager) it is possible to drag and drop windows
between the virtual desktop and the actual workspace.

In Gnome terminology this would mean to be able to
   - click on a window inside the workspace switcher and move it to the 
     current workspace area (outside of the workspace switcher).
     As soon as the mouse leaves the workspace switcher the window would appear
     in full size and you can position it as it would come from the current 
     workspace.

   - It should also be possible to drag a window from the current workspace
     into any of the workspaces visible in the workspace switcher.



Other information:
See olvmw homepage at http://home.nyc.rr.com/twopks/olvwm/