i3 - A dynamic tiling window manager designed for X11, inspired by wmii, and written in C.
Dexpot - If you don't have Dexpot yet, the new update makes it a must-have tool for Windows, adding a ton of features to your desktop that you never knew you wanted.
Xmonad - xmonad is a dynamically tiling X11 window manager that is written and configured in Haskell.
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').
awesome - A dynamic window manager for the X Window System developed in the C and Lua programming languages.
Sysinternals Desktops - Desktops allows you to organize your applications on up to four virtual desktops.