Tutorials were made around the times of Godot 2, which means that there may be a better ways of doing things now (e.g RPC for networking).
Be sure to check them out. You never know what you can find there ;)
And here some tutorials created most likely by me...
- SteamAPI - SteamAPI module in diapers
- Sidescroller Ground Edit - really useful
- Awesome Godot - list of useful plugins, scripts, modules and more!
- Android Admob (Mavhod's or blubee's) - module for displaying ads on mobile devices