instead of giving you my life’s story, here are the links you are looking for
Jack of all trades: OpenGameArt (https://opengameart.org/)
It’d be a crime not to mention open game art, it has just about everything you’d be looking for (with varying levels of quality) this includes sounds, textures, animations, models, and even more. I would be here till my death if I was to list every asset they have.
Polyhaven (https://polyhaven.com/)
If you need high quality natural textures then Polyhaven is the place to go, Polyhaven includes tons of free nature textures, models, and HDRI’s for all of your game development needs. And they aren’t Godot exclusive! You can use these assets in any game engine, but here I will focus on using these things in Godot.
In order to use textures from Polyhaven it’s very simple! All you have to do is choose the texture you want from the browse textures section, choose the texture you’d like, and download all the texture types you’d like to use. Typically, this includes normal-maps, roughness-maps, and emissions if they apply.
Freesound (https://freesound.org/)
This site is exactly what you think it is, if you need some footsteps for your FPS or a car revving its engine for your arcade racer this is exactly where you’d go, although head my warning: not all sounds have the same license to be sure to double-check the license and give credit.
Free music Archive (FMA)
Here is a bit of an obscure one. Free music archive is as close as you can get to finding the perfect music for your particular situation without actually paying someone to make music for you (ouch)
I don’t have anything to say about this personally, but it’s an amazing 100% site!
Obligatory Kenny mention (Assets · Kenney)
Everyone already knows about Kenny, if you don’t, you have certainly seen his assets, he provides many popular assets packs for completely free! This includes stuff like debug textures, gun models, map kits, sounds, and most common things you can think of.
GDquest (https://www.gdquest.com/)
GDquest isn’t just one resource, but a collection of free classes, examples, assets, and even full courses all centered around the ins and out’s of the Godot game engine.
Not only do they have free classes, but they have an infamous resource they call “Learn to code from zero”. This site will teach you not only GDScript, but all the principles needed in order to get started on your programming journey! (Learn to Code From Zero with Godot)
most of all: The Godot discord! (Godot Engine)
Here you can find personally help for every nook and cranny of Godot, beginner or otherwise!
When I find more, I’ll keep this list updated! Don’t be afraid to give suggestions.
If this was helpful to you, maybe check out some of my work, you could grab some inspiration!