FOX Window Manager
A window manager written using the FOX toolkit, providing a clean, stable, and fast window manager primarily for business or professional usage.

Fluxbox
It's based on the Blackbox 0. Yet another windowmanager for X.

sawmill
This is no layer on top of twm, but a wholly new architecture. An extensible window manager using an Emacs Lisp-like scripting language--all window decorations are configurable and all user-interface policy is controlled through the Lisp language.

evilwm
It features no window decorations apart from a simple 1 pixel border, no icons, good keyboard control, including repositioning and maximise toggles. A minimalist window manager for X.

lwm
Lightweight Window Manager: a window manager with no icons, no button bars, no icon docks, no root menus and no configurability.

perlwm
A window manager written in perl! Using perl will allow extra logic to be defined in configuration files.

larswm
A hack for 9wm, adding automatic window tiling and virtual desktops.

aewm
It has no nifty features, but is light on resources and extremely simple in appearance. A minimalist window manager for X11.

Openbox
Openbox is written entirely in C++ and maintains no dependancies on any libraries other than X11. Originally based on Blackbox and currently remains very similar, even using Blackbox styles for its themeing.

CTWM
It supports xpms, multiple workspaces, advanced icon managment, animated icons and backgrounds, 3D titles and borders. Claude's Tab Window Manager: a highly-configurable window manager based on the classic TWM window manager.

amiwm
It is fully functional and can do all the usual window manager stuff, like moving and resizing windows. An X window manager that tries to make your display look and feel like an Amiga® Workbench® screen.

aewm2
aewm2 features keyboard control, Decklin Foster's original menu (and a shell script to generate hierarchical menus), and a rudimentary widget set and datatypes. An X11R6 window manager based on aewm2 and 9wm.

pawm
The Puto Amo Window Manager: a simple and small but nice looking X Window Manager.

WindowLab
As its name suggests, it's something of an experimental window manager and may not suit everyone. A small and simple window manager of novel design.

Enlightenment
) It's designed to be fast, extremely powerful, flexible, configurable, themeable and also usable. A window manager for the X Window System and runs on a UNIX like operating system (like Linux, BSD, Solaris etc.

XSWM
A fast and light window manager for Linux/BSD based on EvilWM.

stwm
Shell-controllable TWM: provides a shell-based interface which enables to operate windows without mouse operation.

yeahwm
A minimalist wm for X based on evilwm.

Waimea
It uses Blackbox image rendering engine (Blackbox styles support) and can use Xrender extension for rendering fonts (anti-aliased font support). A virtual desktop window manager for X11 designed to be fast and highly customizable.

BadWM
A minimalistic window manager for the X Window System licensed under the GNU General Public License that is based on evilwm.

FVWM
An ICCCM compliant multiple virtual desktop window manager for X11 created by Robert Nation and derived originally from twm code.

plwm
It consists of a C module for the basic X functions, and a Python module with the necessary tools to create your own window manager. The Pointless Window Manager: a set of window managing primitives for the Python programming language.

Kahakai
A continuation of Waimea window manager with planned support for extensibility with Python (initially) and Ruby/Perl further down the road.

blwm
A Windows like window manager (in Portugese).

Sapphire
Sapphire also features a small code base written entirely in C++, root menus and window decorations. Small and fast while providing enough features to allow a person to accomplish a variety of tasks with a minimal amount of complexity.

mlvwm
This window manager is developed under FreeBSD 2. A Macintosh like virtual window manager.

VWD
Operates similarly to MS Windows 9x, allowing users to migrate from the Windows platform to the Linux platform without great impact.

B4Step

Window Maker
In every way possible, it reproduces the elegant look and feel of the NEXTSTEP[tm] user interface. An X11 window manager originally designed to provide integration support for the GNUstep Desktop Environment.

Fresco
Fresco extends earlier incarnations to the status of a full windowing system, in command of the video hardware (via GGI, SDL, DirectFB or GLUT) and processing user input directly rather than peering with a host windowing system. A windowing system derived from a powerful structured graphics toolkit originally based on InterViews.

pekwm
Based on aewm++, but has a number of new functions such as window grouping and configurable Rootmenu.

miwm
MIWM is written in C++, for the X window system. Microscopic Window Manager: a minimalist window manager with virtual workspaces.

Piewm
Window manager with pie menus.

WeeWM
A window manager for XFree that is fast, ultra light, all can be done with keyboard.

wmG
It is GTK based and is fully ICCCM compliant, as well as partial Mwm compliance. A window manager for X that is minimalistic, and designed for use with Gnome.

VTWM
VTWM's is user-configurable: The VD's initial scale, size, and position. An extension of TWM, implements a Virtual Desktop that sports a fully-configurable 3D interface.

cwm
It developed out of modifications to evilwm, but eventually the code base of evilwm did not accomodate well for the new features added. A window manager for X11 initially inspired by evilwm.

failsafewm
An extremely minimalistic window manager.

GWM
(Generic Window Manager) is an extensible Window Manager for the X Window System Version 11.

Fluxspace
It can add desktop icons and panels to a pure window manager, such as Fluxbox, by leveraging tools like Rox Filer and Idesk. A window manager and workspace enhancer and integrator.

Ion
It is based on PWM. An unusual kind of window manager that brings a text-editorish, keyboard friendly user interface to window management.

PWM
There are no buttons in the title bar either and only "sloppy" focus mode is supported. A lightweight window manager that does not support icons, memory-exhausting themes or CPU-eating superfluous graphical effects.

Hackedbox
The toolbar and Slit have been removed. A stripped down version of Blackbox.

Matchbox

qlwm
Because it makes heavy use of a high level API it can be kept small, stable and easy to maintain. Yet another window manager for the X11 system.

wm2
Using wm2, you can move windows around the screen, resize windows both horizontally and vertically, hide windows, restore hidden windows and delete windows. A window manager for X.

Interface WM
A highly-extensible window manager written in Objective-C, optimized for use in a GNUstep environment.

NovaWM
NovaWM is developed with speed, size, and style in mind. A new window manager for the X Windows System(X11).

Blackbox
If you have a C++ compiler and the X Window System you can compile and use it. That fast, light window manager you have been looking for without all those annoying library dependancies.

AI-VDi
Artificial Intelligence Voice Desktop Interface: an Open Source Window Manager Project based on KDE.

AfterStep

scwm
Scwm has many, many advanced features, often implemented in the configuration language itself. Scheme Constraints/Configurable Window Manager: a window manager with a powerful dynamic configuration language based on Guile Scheme.

arm0nia project
Our first goal is to create a Dynamic Modular Desktop Environment. A group of projects that intend to create software for making UNIX and UNIX like operating systems, more powerfull and friendly.

TrsWM
The fundamental principles behind this project are the reduction of manual window positioning and the ability to completely manage windows using only the keyboard. Based on Ion.

w9wm
A quick & dirty hack based on 9wm that provides support for virtual screens.

treewm
In addition to the client windows the user can create desktops which can themselves contain windows and desktops. A window manager that tries to implement a new concept.

Lo-Tek
A fast, clean, sexy, and 100% vector theme, in keeping with the Blackbox tradition.

SWM
It was written to speed up working with laptops or even PDA's. Small Window Manager: written for small computer system with very little amount of memory and small screen sizes.

Golem
Design goals are that it be fast and lightweight, as well as very customizable. An X11 Window Manager.

flwm
An X window manager based on wm2 by Chris Cannam, with changes to make it more user-friendly without (I hope) sacrificing any of the clean minimalist design of wm2.

Phluid
It uses rasterman's Imlib2 library as the image/font rendering backend. A window manager that emphasizes efficiency, speed, and beauty.

icewm
It has full GNOME compliance, partial KDE compliance, a default configuration fully usable without tweaking and optional use of mouse. A nice window manager designed for speed, usability and consistency.

Clementine
Clementine is re-written in C++. Based on aewm.

alloywm
alloywm strives for ICCCM compliance, speed, and the a tiny memory footprint. A window manager based on Decklin Foster's aewm.