Linux - LinuxJourney

Linux/system administration - Sad Severs

Programming - LearnXinYminutes

Programming - Lazy Foo's SDL/C++ tutorials (Not sure how practical it would be to learn either of these anymore, but I enjoyed it when I went through)

Vim - vimtutor built in tutorial

Vim - Vim Adventures game to learn Vim's keys

Godot - Heartbeast's tutorials

CSS - Grid Garden

Web Design - Web Design in 4 minutes tutorial

Web Design - Visual design rules you can follow almost every time

SQL - SQLBolt

Guitar - JustinGuitar's Beginner's course (and beyond)

Music theory/guitar - courses from Signals music (many are pay what you want, he also has plenty of good info in his freely available Youtube videos)

Chess - ChessNetwork's beginner to master playlist

Blender - The Donut Tutorial

Pixel Art - Gas 13's tutorial

Pixel Art - Derek Yu's tutorial

2D Art - Drawabox

Japanese - Sakubi's grammar guide

Japanese - Bunpro's grammar references

Japanese - Tae Kim's guide

Smash Melee - melee.cookbook.gg

Melee - Advanced How to Play parts 1, 2, and 3 (outdated, but decent foundational stuff)

Melee - SSBM Tutorials channel

Busuu for language learning. It's like Duolingo, but the main difference is that it actually teaches you the grammar, instead of just making you memorise random sentences. It also has some audio and video of native speakers, at least on the Japanese course. And each module ends with a prompt where you freely write or speak your answer (e.g., "What do you like to eat?") in your target language, and then it gets graded/corrected by native speakers in the community.

And for Japanese kanji specifically, WaniKani. Nothing else I've ever tried has helped with kanji, but their writing style and off-the-wall mnemonics honestly make it so much easier. And you get the first three levels for free, which is actually tons of content.

The nand to tetris course is very good for understanding the fundamentals of computing. Not just basic python, but the very building blocks of computing.

It starts from nand chips, than you build a ram, rom,cpu, and eventually a computer. For that computer you build a ALU and an Assembly like language. Than a complete operating system and a Basic like language. Than a more advanced language that is more akin to OOP and you eventually build tetris.

You can officially find it here, but it's a bit clunky UI. You might be better of finding the course on Udemy or Coursera or something.

Freecodecamp used to help quite a bit.

https://youtube.com/playlist?list=PL4A0248AE2B0DF1A3

I found this series useful when getting into DC electronics. He takes topics very slowly and thoroughly. He's also got a series on oscilloscopes and a more advanced multimeter feature breakdown.

Extremely niche, but https://iidx.org/

This is a single guide that teaches you everything you need to know about how to play Beatmania IIDX, a fun but brutally difficult arcade game. Guide covers everything from setting up a new player profile to clearing the hardest skill challenge in the game, and even includes some music theory

I can't think of anything more helpful than this in terms of relative scale...

I watched this course on cooking knives years ago and I still use a lot of the skills from it. Definitely recommend it if you’re someone who likes to cook: https://www.craftsy.com/class/complete-knife-skills/

https://youtu.be/LiEUnlv2kjU

This guy is very well known already for car audio builds, but this video in particular was nice to have when I thought I destroyed a brand new Focal 165ES K2 speaker. Never gasped so loud in my life as I saw that screwdriver slip straight through the surround.

Biochemistry and Molecular Biology - How Life Works

A lecture series I found on the bay, basically it's third year biochem.

7 hour complete Bash scripting course: https://www.youtube.com/watch?v=Sx9zG7wa4FA

Jazz guitar.

https://www.youtube.com/channel/UCqepSCHTyWj4BzHxEEUNvlg