Mono.Addins is a generic framework for creating extensible applications, and for creating add-ins which extend those applications.
CocosSharp is a C# implementation of the Cocos2D and Cocos3D APIs that runs on any platform where MonoGame runs.
Build & packaging system, responsible for the Mono project distribution for Mac
forked from google/skia
Skia is a complete 2D graphic library for drawing Text, Geometries, and Images.
Gtk# is a Mono/.NET binding to the cross platform Gtk+ GUI toolkit and the foundation of most GUI apps built with Mono