SBSAT is the University of Cincinnati's State-Based Satisfiability Solver.
My first contribution was creating a slider generator, which creates CNF files that cause the SAT solver to explore most of the search space prior to finding a solution.
PSPP is a free, open source alternative to SPSS.
This was the first package I added to MacPorts, and began providing installers for older Mac systems since.
I've been contributing to the MacPorts project since I joined in 2009.
During that time, each year I mentored in Google's Summer of Code:
The first port I ever maintained was PSPP, and since then I've picked up several other packages as I addressed tickets and used open source software—sometimes creating new ports of them for the Mac.
I now maintain over 150 packages.
I've also helped push modifications to the core of MacPorts including SHA256 checksums and binary archives, all of which went live with MacPorts 2.0.