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.
i3 is a dynamic tiling window manager. Its key features are correct implementation of Xinerama (workspaces are assigned to virtual screens, and it does the right thing when attaching new monitors) and XrandR support (which is still unfinished). Both horizontal and vertical columns can be used in tiling. There is a special focus is on writing clean, readable, and well documented code. i3 uses xcb for asynchronous communication with X11, and has several measures to be very fast. i3 is primarily targeted at advanced users and developers.
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.
GNUSTEP Live CD contains a lot of software for GNUstep, a free implementation of the OPENSTEP framework (which is also directly used in Mac OS X as Cocoa). It includes excellent applications for RAD (GORM and ProjectCenter). The CD is available for i486, AMD64, Apple Mac PowerPC, and Sun UltraSPARC computers.
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. When appropriate, the pointer is also constrained to the taskbar/menubar in order to make target menu items easier to hit.
awesome is a highly configurable, next generation framework window manager for X. It is very fast, light, and extensible. It is primarily targeted at the power user, developer, and anyone dealing with everyday computing tasks who wants to have fine-grained control over a graphical environment.
IceWM Control Panel is a full-featured, GTK-based control panel for IceWM. It features an IceWM theme designer, Ice Sound Manager (for sound events), IcePref2, and tools to manage desktop wallpaper, cursors, keys, window options, and more. IceWM Control Panel has a familiar, Windows-like Control Panel user interface.