Tri-Desk-A-Top is a simple, lightweight and easy-to-use virtual desktop manager.
Running the program adds three icons to your system tray, numbered 1, 2 and 3. Each of these represents a separate desktop with its own applications and window arrangements, and clicking an icon instantly switches you to that desktop.
You can alternatively cycle through the desktops by holding down Ctrl+Win and pressing the Plus or Minus keys.
It's also possible to move applications from one desktop to another, either by the mouse (right-click that desktop icon, choose the application and its destination) or the keyboard (select the application, hold down Ctrl+Win and press the number of the destination desktop on the numeric keypad).
That's essentially it for features, but there's enough power to be useful, and it does mean the program is relatively lightweight at under 4MB RAM.
There are no clever extras here, no options to, say, make one application visible on multiple desktops. But Tri-Desk-A-Top is also no-strings free, delivers the core virtual basics well, and is so simple that you'll have mastered it in maybe 5 minutes. If not less.