First off, if you've never heard of it, the Godot Engine is a cross platform, open source C++ based, Unity-esque game engine that runs on Mac, Windows and LInux and targets those plus iOS, Android and more. For an overview of the engine you can start here.
... anyways, one of the major downsides is the lack of documentation, so I've set about creating a tutorial series. Starting from day one this series includes both video and text tutorials.
The series table of contents is available right here. Right now the series covers graphics, audio, input, life cycle, UI and more. Eventually I hope to cover all aspects of Godot development. So expect more tutorials soon. Also, for each video tutorial, keep in mind the video on YouTube is available in 1080p, while the embedded version is much lower resolution.
If you've never checked it out and want to try a game engine with a full suite of tools included, be sure to give it a shot, it may surprise you. Of course, free and open source is always nice!