Lunchbox is a dynamic tiling window manager for X11. It allows windows to be resized by squishing them against the edge of the screen. In a step away from the desktop metaphor, all programs are given a separate workspace and unique arrangement of windows, and any window can become the desktop. It offers an in-built scalable tab replacement called the Title Menu, which allows any window to be swapped with any other window that fits, allowing very fine grained control over the layout of the screen. Finally, although many windows default to tiling, any window can be changed to a Floating mode, which dialog boxes default to.
wumwum is a window manager manager. The idea behind wumwum is to turn any EWMH-compliant window manager into a tiling manager a la "ion" or "awesome". wumwum works by using wmctrl, and adapts itself dynamically to the active window manager. All functionality from the underlying window manager is kept when under wumwum, making it ideal for beginners.
GOULD (GTK+ Objects Ultra Light Desktop) is an ultra-light desktop environment. Tt provides gpanel, a configurable desktop panel with a built-in shortcuts manager, gdisplay, an image viewer with a directory browser, gsnapshot, for screen, window, and region capture, and grdesktop, an rdesktop front-end.
X Persistent Remote Applications (xpra) is "screen for X". It lets you run applications remotely (like ordinary X or VNC), but unlike ordinary X, these applications are "persistent" if you lose your connection, or even if you want to switch to another computer. Also unlike VNC, they are ordinary applications on your desktop managed by your window manager, not trapped in a box.
Wimpiggy is a library for writing EWMH-compliant, compositing window managers using Python and GTK+. The goal is to make writing a window manager as easy as writing a PyGTK application. This library can be used to build a trivial, working window manager in only about 40 lines of code.