Cairo Shell - Cairo is a desktop environment for Windows.
i3 - A dynamic tiling window manager designed for X11, inspired by wmii, and written in C.
Talisman Desktop - Talisman Desktop is a configurable Windows shell replacement introduced in 1997 by Lighttek...
dwm - dwm is a dynamic window manager for X. It manages windows in tiled, monocle and floating layouts. All of the layouts can be applied dynamically, optimising the environment for the application in use and the task performed.
bbLean - Alternative Windows shell
Openbox - Openbox is a highly configurable, next generation window manager with extensive standards support.