GtkGLMaterialDialogis a GTK+ dialog that can be used to edit 3D-object material properties. It is based on the material properties of OpenGL with diffuse, ambient, specular, emissive colors (RGBA), and a specular coefficient (shininess). The material is previewed by rendering a lit OpenGL sphere in a gtkglarea widget.
GQuiz is a generic question/answer drilling program. You provide a program that displays the question and answer, given as a single filename on the command line, and gquiz randomizes, prevents immediate repetition, and temporarily eliminates questions you've answered correctly "enough" times in a row. The author uses GQuiz with cgoban to study go, the Asian strategy game, but it could just as well be used to memorize States and their Capitals, or foreign language vocabulary, etc.