Single header only C++ logging library. It is extremely light-weight, robust, fast performing, thread and type safe and consists of many built-in features. It provides ability to write logs in your own customized format. It also provide support for logging your classes, third-party libraries, STL and third-party containers etc. 

Introducing Garnet – an open-source, next-generation, faster cache-store for accelerating applications and services

Missing Silverlight and Waiting for Blazor? CSHTML5 for C# Web Development Goes Open Source 

How Microsoft rewrote its C# compiler in C# and made it open source 

The best IDE for building React Native
apps is now free and open source

A web site that helps you discover awesome .NET open source and community resources  

Piranha CMS - The Open source CMS for .NET Core, NetStandard and AspNetCore MVC