i3 - A dynamic tiling window manager designed for X11, inspired by wmii, and written in C.
Fluxbox - Fluxbox is a window manager for X that was based on the Blackbox 0.61.1 code.
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.
IceWM - icewm home page . Bug Tracking. If you have a patch, a bug report or a feature request to submit, please do so at the icewm project page at SourceForge.
awesome - A dynamic window manager for the X Window System developed in the C and Lua programming languages.
JWM - Also known as Joe's Window Manager. Created in 2003, one of the default window manager for Puppy Linux, and actively updated by Joe, its creator.