I'm a big fan of Getting Things Done (GTD) by David Allen. After years of keeping my next actions and projects in Outlook, I moved to the simpler Todo.txt format. I loved the idea of the todo.sh script for easily working with the Todo.txt format from the command line, but I'm mostly a Windows guy. Rather than install Cygwin, I created a version of the command line interface in Powershell. I also like to have my todo lists available on my phone, so I created a version for Windows Phone 7 (now available on the Marketplace). Both projects parse the text files using a .NET library I created.
I've worked on a couple of projects which use HipChat for collaboration, and I wanted a helpful chatbot to handle some tasks. So I contributed to XmppBot-for-HipChat and wrote several plugins to extend it.
I also created a library to make converting between units of measurement easier, especially when dealing with different systems and inconsistent names and abbreviations.
You can also find my contributions to other open source projects via my accounts on GitHub and CodePlex.
In addition to open source work in communities like CodePlex and GitHub, I'm also active on StackOverflow amd Programmers StackExchange.
In 2011 I gave a talk at the BSUG - Reactive Extensions and Remote Automation with Windows Phone 7. Materials from the talk can be found here.
I also occasionally write about programming stuff on the CodeWise blog.