aewm is a minimalist window manager for X11. It has no nifty features, but is light on resources and extremely simple in appearance. It should eventually make a good reference implementation of the ICCCM. A few separate programs are included to handle running programs, switching between windows, etc.
Athene is a desktop system for Linux that uses its own graphics drivers for high speed access to your graphics card. Because the Athene desktop and its applications have direct access to the graphics hardware, they have a significant speed advantage over conventional X applications. Athene is also backwards compatible with your existing X11 software. It features a highly responsive interface, scalable icons, translucency, alpha blending, Unicode support, and Windows compatibility.
Blackbox is yet another addition to the list of window managers for X. It is written in C++, sharing no common code with any other window manager (even though the graphics implementation is similar to that of WindowMaker). It features small code size, a fast interface with simple menus, multiple workspaces, decorated windows, built-in graphics code to render solids, gradients, and bevels on the fly, and more.
CTWM is a highly-configurable window manager based on the classic TWM window manager. It supports xpms, multiple workspaces, advanced icon managment, animated icons and backgrounds, 3D titles and borders, etc. It offers rudimentary Gnome support and is backwards-compatible with TWM.
Enlightenment is a themeable, fast, flexible, and powerful window manager that is designed to be as configurable as possible in both look and feel. In addition, Enlightenment provides an applet API that provides functionality somewhere between the GNOME applet system and Dock Apps from Afterstep/WindowMaker. The current design aim is for Enlightenment to become a desktop shell.
FvwmPartition is a FVWM2 module that allows the user to build a structure of panes in a fairly arbitrary manner. Windows can be attached to these panes and manipulated together by dragging the bars that separate the panes. Windows in a specific pane can selected by tapping the labels on the parent bar or moved by drag-and-dropping the labels.