This is links to libraries, all open source that’s relevant to game programming development and MonoGame/XNA.

1. Awesome MonoGame. Covers General, Engines, Tiles, Animations, Audio, User Interfaces, Interop, Physics,Artificial Intelligence, Effects, Consoles, Pipeline, AR/VR, Networking, Helpers and Samples.
2. Top 27 MonoGame Projects. This includes a few game engines.
3. Open VIII. A reimplementation of Final Fantasy VIII for Windows and Linux but will go Mobile eventually.