VirtuaWin - VirtuaWin is a virtual desktop manager for the Windows operating system (Win9x/ME/NT/Win2K/XP/Win2003/Vista/Win7/Win10). A virtual desktop manager lets you organize applications over several virtual desktops (also called 'workspaces').
Sysinternals Desktops - Desktops allows you to organize your applications on up to four virtual desktops.
9Desks - up to nine virtual desktops
TotalSpaces - TotalSpaces provides a grid of spaces on OSX Lion
Virtual Dimension - Virtual Dimension is a free, fast, and feature-full virtual desktop manager for Windows platform.
Cairo Shell - Cairo is a desktop environment for Windows.