Lumix Engine - Open source 3D game designer and engine written in C++.
Mac Mouse Fix - A simple way to make your 3rd party mouse better.
Grit Game Engine - The Grit Game Engine is an MIT-Licensed Open Source Game Engine that is highly scriptable via Lua.
Smooze - Smooze animates your scroll and adds functionality to your non-Apple mouse (scroll-wheel mouse).
Pygame - Pygame is a set of Python modules designed for writing games.
Smart Scroll - Smart Scroll makes scrolling smoother, faster and more comfortable: