Features:   

• virtual Desktops/Workspaces for Windows Vista/XP/2000 *
• integration into the panel
• move windows between the Desktops by drag 'n drop or by using the windows menu
• optional Keyboard Shortcuts for switching the Desktop
• Set a window "sticky": always visible
• "Mini-Windows"  give an overview from each Desktop
• On Screen Display (OSD)  for the current Desktop number
• automatic Desktop switching  if a window from another Desktop is requested
• support for "Flashing-Windows" (notify for new messages in Mirc for example)
• keep a window above all others by selecting "Always on top" from the windows-menu
• no administrator rights necessary
• no installation 

*: Vista: black panel; XP: blue panel theme

Sad: Desktop Switcher from http://www.speedapps.com is a one-to-one copy from Windowspager. Even the text and the screenshots are stolen. Speedapps is violating my copyright and the GPL (the source is not available, no contact informations).