transset-df is a heavily patched version of xorg's transset. It is used to set the transparency of windows in X with the xcomposite extension. It adds several command line options to make it easier to use directly, bound to hot keys in your window manager, or through scripts. These include the ability to select a window by window ID.
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.
WnDO (formerly Fbdo) is a small suite of complementary tools for adding behavioral extensions to Gnome, Xfce, Fluxbox, and other window managers. WnDO offers a plugin platform for tweaking the desktop environment. It focuses on modifying behavior, rather than adding desktop widgets. It has minimal dependencies, other than Python. Included modules handle window alignment, simple window tiling, process management, wallpaper management, and custom keyboard shortcuts. Wallpaper management capabilities include per-workspace and randomly-selected wallpaper. It performs its own key grabbing in order to avoid interaction and conflict with the equivalent window manager facility. It requires CmDO.