GtkGLArea is an OpenGL widget for GTK+ GUI toolkit.
GtkGLArea provides gdkgl, a wrapper around GLX functions, which is similar to the GDK that GTK+ is built upon.
The widget itself is derived from GtkDrawingArea widget.
A number of application use this widget:
Celestia -- Real-time visual simulation of space
fsv -- 3D File System Visualizer
Gcad -- Simple 2D CAD application for GNOME
Ghemical -- Molecular modelling package
glChess -- 3D chess interface
Morpheus -- 3D Model viewer for GNOME desktop
Xtraceroute -- Shows path of IP packets graphically
It can be found online at http://www.student.oulu.fi/~jlof/gtkglarea/.