XWidglets is a complete rich Java Swing tool for designing, creating, and using XML-based GUIs. It provides a lightweight XML client, clear separation between view, data, and process, MVC I and II support, event management, a consistent look and feel across platforms, a rich set of GUI components, and n-tier architecture integration.
xlax is an X11 input multiplexer: it sends your keyboard input from the xlax window to a group of windows simultaneously. The tool is designed for system administrators who typically have to do the same thing on several machines (or in several different directories). Windows can be added or deleted interactively, or temporarily disconnected and reconnected. xlax allows you to assign a custom string to each window (e.g. a hostname) that can be sent with a button click. An included script handles starting up and arranging windows, and allows you to set up commonly used window groupings in a config file.
xoris grabs the RGB color value of any pixel on the screen and dumps the color's name to stdout. The output can be printed either as hex (#b0958e), as a triple of decimal RGB values (229 229 229), or as an abstract name (gray90). xoris has only been tested on displays with a bit depth of 24 bpp.
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.