Tcl provides a portable scripting environment for Unix, Windows, and Macintosh that supports string processing and pattern matching, native file system access, shell-like control over other programs, TCP/IP networking, timers, and event-driven I/O. Tcl has traditional programming constructs like variables, loops, procedures, namespaces, error handling, script packages, and dynamic loading of DLLs. Tk provides portable GUIs on UNIX, Windows, and Macintosh. A powerful widget set and the concise scripting interface to Tk make it a breeze to develop sophisticated user interfaces.
Zune is a free clone of the famous MUI (Magic User Interface) toolkit from the Amiga. It is primarily designed for C, and uses BOOPSI as an object-oriented layer. The MUI-apps developer should not care about "precise" graphic design (to let the user fully customize its application), and not care about resize (smart automatic layout algorithm). The MUI-apps user has maximum control over applications look and feel, and he can customize apps either globally or individually through a graphical prefs program.
GTK, which stands for the Gimp ToolKit, is a library for creating graphical user interfaces. It is designed to be small and efficient, but still flexible enough to allow the programmer freedom in the interfaces created. GTK provides some unique features over standard widget libraries.
WebGUI is a content management framework built to allow average business users to build and maintain complex Web sites. It is modular, pluggable, and platform independent. It was designed to allow the people who create the content to manage it online, rather than content management taking up the time of busy IT staff. WebGUI comes with a full host of features including shopping cart, subscriptions, forums, photo galleries, FAQs, link lists, blogs, SQL reports, a Web services interface, and a very configurable user privilege and profiling system.
The Xmt Library provides nine custom widgets and over 260 convenience functions designed to make Motif user interface development easier for beginning and advanced programmers. It provides an alternative tool chain that avoids the use of GUI builders. The essence of this approach is to program from the resources file using an extended vocabulary for automatic creation of the widget hierarchy, dynamic layout, and to provide a rapid prototype environment.
Tkinter is Python's de facto standard GUI (Graphical User Interface) package. It is a thin object-oriented layer on top of Tcl/Tk. To use Tkinter, you don't need to write Tcl code, but you will need to consult the Tk documentation and occasionally the Tcl documentation (since Tk's low-level event handling mechanism is considered part of Tcl).