Here are some of the major software projects that I'm working on (or have worked on in the past). They are all free and open source (for the most part, under the terms of GPLv3), in the hopes that somone else might find them useful. If so, let me know; I'd love to hear how you used it!
Tsukurou! is a libre software initiative that I founded to develop a framework for games based in a voxel world. The name translates roughly to "Let's Build!" in English, which highlights the project's primary goals: to provide an unlimited sandbox world for players to build in, and to provide unlimited opportunities to the developers who make the games.
Strongback is an open-source library designed by and for FRC students. It is designed to promote testability of the robot functionality through test suites can run without access to actual robot hardware. I am one of the founders and maintainers of the project, in addition to other maintainers from team 4931 and contributors from several other teams.
Samurai IRC Bot
When I first started programming seriously, I also began studying the IRC protocols. I hosted my own IRC server and messed around with it. I also wrote a few IRC clients; the only one that turned into a full project was Samurai. It is a runtime written in Java that provides a framework for IRC bot development. It handles the connection to the IRC server and command parsing and manages the event system and plugin loader. Plugins get loaded dynamically at runtime (inspired by the Bukkit plugin loader) and provide the functionality (commands etc.).
While I'm not currently adding new features, I still maintain it for stability. I currently have an instance deployed on my production IRC server (irc.nonemu.ninja) that hosts plugins for the Open Redstone Engineers community.