twin is a text-mode windowing environment: it draws and manages text windows on a text-mode display, like X11 does for graphical windows. It has a built-in window manager and terminal emulator, and can be used as server for remote clients in the same style as X11. It can display on Linux console, on X11 and inside itself.
spectrwm
sscrotwm Shriveled scrotwm is a minimalist fork of scrotwm/spectrwm.
AHWM - Alex Hioreanu's Window Manager
goomwwm: Get out of my way, Window Manager!
JWM (Joe's Window Manager) license: GNU GPL.
i3 is a tiling window manager, completely written from scratch. The target platforms are GNU/Linux and BSD operating systems, the code is Free and Open Source Software (FOSS) under the BSD license. i3 is primarily targeted at advanced users and developers.
AfterStep is a window manager for the Unix X Window System. Originally based on the look and feel of the NeXTStep interface.
AltDrag gives you the ability to move and resize your windows in a new way. When running, you can simply keep the Alt key depressed and then click and drag any window. Besides just moving windows, you can resize, maximize and close them too. AltDrag simply allows you to do more with less mouse movements. (License: GNU GPL v3, Code: Github)