I am a professional programmer with years of experience. I've written fairly substantial portions of a number of products.
I also find myself optimizing my own life or hacking on something for fun. The nice part about hacking on something for fun is that I can try out things that may fail in a particularly amusing fashion.
Some projects I've worked on over time:
I spent a bunch of time working on this in the 2000-2001 timeframe. Before you could do procedural shading in the GPU, I had implemented it by generating bitmap textures. I also wrote a bunch of physics simulation code for a flight model, real-time continuous level of detail terrain, and a bunch of utility libraries. I also wrote an audio library.
I stopped hacking on it and it's basically obsolete at this point.
As a college project, I wrote a global illumination rendering engine using photon mapping.
A joystick controlled filter for live performance in Buzz.