Fizzim is a finite state machine compiler, the latest version (9 years old!) converted a state machine drawn in Dia to C++ code.
The Insect AI demos I made for AI Wisdom.
The simple Physics Engine described in my Game Engine Gems article.
Various old engine components.
Also includes the beginnings of an old level editor using FLTK from back when FLTK was all the rage with VFX houses.