"Molten Core" is a core library for .NET applications. It fills in a few gaps with the .NET framework and provides reusable functionality for apps. It includes, for example, basic MVVM support for WPF applications (including commands, converters, and a bindable base class), application mutexing and updating (when using ClickOnce), and more.
Planning Poker is a web application designed to allow agile teams to vote on levels of effort for work items. The game is based on the card game of the same name, although this version provides more flexibility. The client is entirely web-based, and the server is written in C#. There is also a server manager application which can keep track of multiple game servers and automatically start and stop them using a web interface.
SharpHue is a wrapper library for the Philips Hue lighting system. Developers using this library are able to control lights using familiar C# coding techniques such as collections, indexing, and method chaining. This library has gained mild attention due to its listing on the official Hue Developers site.