itch.io

I'm probably either going to be using Godot Engine (https://godotengine.org/) or Adventure Game Studio (http://www.adventuregamestudio.co.uk/) depending on which idea I end up implementing (currently brainstorming/mind-mapping/etc, I've narrowed it down to three ideas). Both are open-source.

https://github.com/Calinou/awesome-gamedev is one I've seen posted a lot.

Edit: Looks like I was too slow, and two others have posted this first. Kudos to those who replied first, I guess that's a sign of how good this list actually is