A simple calculator app, not as nice as the free one that comes with Windows. This was originally released at http://zetacentauri.com and was downloaded more than 5000 times before being open sourced.
A prebuilt Windows installer is available in the installer directory:
This application is no longer actively maintained, and I'm unlikely to accept pull requests. It was more of an experiment to build a basic calculator using C# than a serious product.