If you're tired with all those modern "feature-rich" WMs and just need a simple and convinient tool to manage your windows with low memory footprint, you should definitely look into the following list:
1. aewm
aewm is a well-known minimal window manager for X11, one of the oldest. It has few features, but is light on resources and extremely simple in appearance. It aims to be a sane, readable, hackable implementation of the important parts of the ICCCM and EWMH (but not all of them). aewm was based on 9wm and has in turn inspired quite a lot of other simplistic window managers, like aewm++, alloywm, evilwm, WindowLab, wimpwm and so on...
2. Ion
Designed to be primarily used from the keyboard, Ion was written as an experiment on a different kind of window management model. It tries to address the navigation problem by dividing the screen into mutually non-overlapping frames that take up the whole screen. Big displays have so much space that this should be convenient and smaller displays couldn't show more than one window at a time anyway. The frame layout is, of course, dynamic and different on each workspace. Given the organised tree based instead of an unorganised coordinate-based frame layout, moving between the frames can be conveniently done from the keyboard. As in PWM, the frames may have multiple clients attached, each indicated with a tab.
3. Sawfish
Sawfish is an extensible window manager using a Lisp-based scripting language --all window decorations are configurable and all user-interface policy is controlled through the extension language. Despite this extensibility its policy is very minimal compared to most window managers. Its aim is simply to manage windows in the most flexible and attractive manner possible. As such it does not implement desktop backgrounds, applications docks, or other things that may be achieved through separate applications.
4. dwm
dwm is a fast and simple window manager for X11. It manages windows in tiling and floating modes. Either mode can be applied dynamically, optimizing the environment for the application in use and the task performed. Windows can be tagged with one or multiple tags. Selecting certain tags displays all windows that are accordingly tagged.
5. awesome
awesome is a tiling window manager initialy based on a dwm code rewriting. It's extremely fast, small, dynamic and awesome. Windows can be managed in several layouts: tiled and floating. Each layout can be applied on the fly, optimizing the environment for the application in use and the task performed.
Managing windows in tiled mode assures that no space will be waste on your screen. No gaps, no overlap. With tiled layout, windows are managed in a master and a stacking area. The master area contains the windows which currently need most attention, whereas the stacking area contains all other windows. The master area can be splited in several rows and column, as you want. In floating layout, windows can be resized and moved freely, just like a usual window manager. Dialog windows are always managed floating, regardless of the layout selected.
Windows are grouped by tags. Each window can be tagged with one or multiple tags. Selecting certain tags displays all windows with those tags. Each tag can have its own layout. Tags can be compared to virtual desktops, but it's more powerful: you can quickly merge and show several tags at the same time, and go back to only one tag after.
6. Karmen
Karmen is an easy-to-use window manager for X, written by Johan Veenhuizen. It is designed to “just work”. There is no configuration file and no library dependencies other than Xlib. The input focus model is click-to-focus. Karmen aims at ICCCM and EWMH compliance. The current version is Karmen 0.13, released September 4, 2007.
7. evilwm
evilwm is a minimalist window manager for the X Window System. 'Minimalist' here doesn't mean it's too bare to be usable - it just means it omits a lot of the stuff that make other window managers unusable. It has no icons and no window decorations apart from a simple 1 pixel border. Provides good keyboard control, including repositioning and maximise toggles, snap-to-border support and virtual desktops. evilwm has extremely small binary size (even with everything turned on).
8. larswm
larswm is a rewrite of 9wm that adds automatic tiling, virtual desktops and many more features to make it a highly productive user environment. Despite the high level of automation, it uses very little CPU time and memory while running.
9. WindowLab
WindowLab is a small and simple window manager of novel design. It has a click-to-focus but not raise-on-focus policy, a window resizing mechanism that allows one or many edges of a window to be changed in one action, and an innovative menubar that shares the same part of the screen as the taskbar. Window titlebars are prevented from going off the edge of the screen by constraining the mouse pointer, and when appropriate the pointer is also constrained to the taskbar/menubar in order to make target menu items easier to hit.
10.Anarchy
Anarchy is a window manager for the X Window System and is implemented in less than 500 lines of CLOS oriented Scheme code.Despite its small code size, it supports most functions expected of a basic window manager (move, resize, hide, minimize, maximize, list windows, root menu).
