Unfortunately, most of my projects are not (currently) open-source, but two of the more interesting open-source projects I’ve meaningfully contributed to in the past include:

You can see a full list of everything I’m actively working on in my by visiting my Bitbucket and GitHub accounts.

On the closed-source front, the biggest project I worked on in the past was at Fog Creek, where I worked heavily on Kiln, a cutting-edge DVCS hosting solution initially based on Mercurial, and later allowing each member of a team to make their own choice between Mercurial and Git on a commit-by-commit basis—the only tool to provide such functionality. Way back at the beginning of my career, I worked on Fog Creek Copilot, a remote assistance solution for micro-ISVs.