i3 - A dynamic tiling window manager designed for X11, inspired by wmii, and written in C.
DisplayFusion - DisplayFusion will make your multi-monitor life much easier.
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.
Mizage Divvy - Divvy is an entirely new way of managing your workspace.
Openbox - Openbox is a highly configurable, next generation window manager with extensive standards support.
WindowGrid - Quickly and easily layout windows on a dynamic grid using just the mouse.