a free user interface builder for GTK+ and GNOME, using libglade, Glade XML files can be used in numerous programming languages including C, C++, Java, Perl, Python, C#, Pike, Ruby, Haskell, Objective Caml and Scheme. Adding support for other languages is
(pronounced "fulltick") is a cross-platform C++ GUI toolkit for UNIX®/Linux® (X11), Microsoft® Windows®, and MacOS® X. FLTK provides modern GUI functionality without the bloat and supports 3D graphics via OpenGL® and its built-in GLUT emulation.
a free user interface builder for GTK+ and GNOME interfaces designed are saved as XML, and by using the libglade library these can be loaded by applications dynamically as needed. (Glade can also generate C code)
port of the X Window System server to Windows. It shares the same source code base as Cygwin/X, but does not depend on the Cygwin environment or cygwin1.dll. Xming is a fully featured X11 server for Windows that is very simple to install and use.