qtile!

Openbox is a highly configurable, next generation window manager with extensive standards support.

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.

Bluetile is a tiling window manager for Linux, designed to integrate with the GNOME desktop environment. It provides both a traditional, stacking layout mode as well as tiling layouts where windows are arranged to use the entire screen without overlapping. Bluetile tries to make the tiling paradigm easily accessible to users coming from traditional window managers by drawing on known conventions and providing both mouse and keyboard access for all features.

Fluxbox is a windowmanager for X that was based on the Blackbox 0.61.1 code. It is very light on resources and easy to handle but yet full of features to make an easy, and extremely fast, desktop experience. It is built using C++ and licensed under the MIT-License.

spectrwm is a small dynamic tiling window manager for X11. It tries to stay out of the way so that valuable screen real estate can be used for much more important stuff. It has sane defaults and does not require one to learn a language to do any configuration. It was written by hackers for hackers and it strives to be small, compact and fast.

xmonad is a dynamically tiling X11 window manager that is written and configured in Haskell. In a normal WM, you spend half your time aligning and searching for windows. xmonad makes work easier, by automating this.

herbstluftwm is a manual tiling window manager for X11 using Xlib and Glib.

wmii is a small, dynamic window manager for X11. It is scriptable, has a 9p filesystem interface and supports classic and tiling (acme-like) window management. It aims to maintain a small and clean (read hackable and beautiful) codebase.

pekwm is a window manager that once up on a time was based on the aewm++ window manager, but it has evolved enough that it no longer resembles aewm++ at all. It has a much expanded feature-set, including window grouping (similar to ion, pwm, or fluxbox), autoproperties, xinerama, keygrabber that supports keychains, and much more.

WMFS² is a lightweight and highly configurable tiling window manager for X written in C. WMFS² is a free software distributed under the BSD license. It can be driven from keyboard or mouse and its configuration stands in one text file, easily understandable.

Ratpoison is a simple window manager with no fat library dependencies, no fancy graphics, no window decorations, and no rodent dependence. The screen can be split into non-overlapping frames. All windows are kept maximized inside their frames to take full advantage of your precious screen real estate. All interaction with the window manager is done through keystrokes.