I have written or worked on several pieces of publicly available software.
Lyybnyz is a library in the Common Lisp programming language for manipulating directed graphs while maintaining them in minimized form. It is a new prototype based on an unreviewed algorithm; I wrote it myself.
SBCL is a compiler for the Common Lisp programming language. It is a reasonably mature and decidedly ancient system; it is derived from code written at Carnegie Mellon University in the 1980s. I don't work on it much now, but at one point I did some serious work to make the old code base easier to work with, and various work to fix bugs and improve compliance with the ANSI standard, and I still head the group of developers on SourceForge who continue to improve it.
I wrote (as the team "Busman Holiday Club," which turned out to be just me) an entry in Common Lisp for the Lightning division of the 2004 ICFP Programming Contest.
I wrote and released a reasonably simple C++ program to play the game of Go, "wally", based on an older assembly language program of the same name described in Byte magazine. It was not a strong player, but for a while it was a popular trivial opponent for people to test their programs and algorithms (especially machine-learning algorithms, it seemed) against.