Provide Unix and Java GUI builder tools such as JClass, JProbe, UIM/X, db-UIM/X, XRT and Platinum.

A rich thin client framework for building software applications that combine the usability and speed of desktop software GUI with the centralized administration and universal accessibility of Web apps.

A cross-platform C++ based Toolkit for developing GUIs easily and effectively (Unix/X, Win32). [Open source, LGPL]

Project that aims to develop a reliable, stable and fast graphics system that works everywhere which will allow any program using GGI to run on any platform requiring at most a recompile.

Full windowing and rich client framework written in JavaScript enables full featured application solutions to run in just a standard browser with astoundingly rapid development and deployment ease.

A platform independent graphical user interface library developed specifically for games.

Toolkit for cross-platform GUI programming on Windows, X-Windows, Linux and Macintosh systems. It works with the C, C++ and Python languages, and the source code can be freely downloaded here.

The PEG GUI library home page. PEG is a C++ GUI library designed exclusively for real time embedded systems.

A cross-plataform, easy-to-use, non-intrusive C++ GUI library that runs on top of SDL. [Open source, LGPL]

Based on the Simple DirectMedia Layer (SDL). Allows to put together portable graphical applications.