KWin!

Dexpot turns your monitor into up to 20. It creates and manages virtual desktops and enables you to work far more efficiently and comfortably with many simultaneously opened windows on Windows 95/98/ME and NT4/2000/XP/2003/Vista (incl. x64).

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’). Virtual desktops are very common in Unix/Linux, and once you get accustomed to using them, they become an essential part of a productive workflow.

WinSplit Revolution is a small utility which allows you to easily organize your open windows by tiling, resizing and positioning them to make the best use of your desktop real estate.

Preme is a free software for Windows which lets you add cool desktop features and enhances the desktop functionality.

Adds eye-candy effects to windows (and start menu) like deformations (e.g: jelly windows - that makes moved window wiggle like being made from jelly; or fold - which hides windows by folding up horizontally, and unfolds when showing), physics (e.g.: keep momentum - making window to conserve move momentum; or bounce - that makes windows bounce upon receving focus ) and other SFX (e.g.: pixie dust - which makes moved window to leave a trail of twinkling pixie dust; or close puff - which displays puff cloud below cursor when closing window). »

TotalSpaces provides a grid of spaces on OSX Lion

Mission Control, formerly Exposé, is a feature of the OS X operating system.

Bluetile is a tiling window manager for Linux, designed to integrate with the GNOME desktop environment. It provides both a traditional, stacking layout mode as well as tiling layouts where windows are arranged to use the entire screen without overlapping. Bluetile tries to make the tiling paradigm easily accessible to users coming from traditional window managers by drawing on known conventions and providing both mouse and keyboard access for all features.

Chameleon Window Manager will allow you to control the windows of your programs using customizable buttons added to the title bars of the windows (Always on Top, Minimize to Tray, Minimize to Caption, Specify Transparency, Position window at left/right of screen).The interface supports skins and is very easy to use.

Virtuoz was designed to be a minimal and robust program that allows to have more than one desktop on Windows. It was inspired by Sysinternals Desktops, but uses a different approach, which doesn’t impose the limitations which Desktops is bound to.

Skippy-XD is a full-screen task-switcher for X11. You know that thing Mac OS X, Compiz and KWin do where you press a hotkey and suddenly you see miniature versions of all your windows at once? Skippy-XD does just that. It's most commonly known by Mac OS X's name for it - Exposé.

GiMeSpace Desktop Extenders are scrolling virtual desktop managers and the only virtual desktop/window managers that give you seamless unlimited desktop space. New since version 2 is that you can now also resize your windows without any limitations. You can have for example a window that is 16000x16000 pixels wide. No screen will ever have that resolution!These programs make the panning (pan and scan) function that so many users liked in windows XP available for windows Vista and Windows 7. But now in a more powerful and flexible way!New since version 2.1 is that you can limit the size of your virtual desktop to the space that is used by your application windows. If you use only the space within you visible screen you will not even notice that GiMeSpace is running!All versions require windows XP or later versions except the 3D version that requires Windows Vista or 7 with Aero theme. 64bits is supported since version 2.2. »

mDesktop is a lightweight application that allows the user to utilize multiple virtual desktops. Also, mDesktop integrates with Hotcorners. mDesktop currently supports up to ten virtual desktops.