Solve puzzles. Learn CUDA.

Learning GPU programming ideas by solving coding puzzles step-by-step. Seems really neat, especially that it uses python so you can focus on the actual ideas instead of syntax, etc.

A video solving some of the early puzzles can be found here

An interesting series of video lessons matching programming instructions and algorithms with processor architectures and assembly equivalents.

NOT free!

An amazing introductory book for jujutsu

Extensive explanations of how to attribute CC licenses, for different kinds of media, for straight usage, for modifications and more.

Very in-depth and a good resource.

An exhaustive guide on researching user needs (intended for products but equally applicable to other consumption-facing processes).

Very neat and condensed collection of thoughts about interview- and observation-style research.

Nice to learn how to make pynvim and lua interoperate for neovim.

An exhaustively detailed (and example-oriented) tutorial on creating template files for voidlinux and making sure that they work.

Even goes into different build systems, contributing your changes upstream and more.

Are you looking to enhance your data skills and become proficient in SQL? We just posted a comprehensive, 11-hour SQL course on the freeCodeCamp.org YouTube channel. It will teach you to handle complex database queries. (Vlad Gheorghe)

A giant course going over many of the 'functions' of SQL. Good but long, and you will need to consult additional sources to connect many of the concepts to the bigger picture.

An open-source guide to help you write better command-line programs, taking traditional UNIX principles and updating them for the modern day.

Long, in-depth and very fascinating. I think everyone can take something useful away from this.

Curious exactly what happens when you run a program on your computer? Learn how multiprocessing works, what system calls really are, how computers manage memory with hardware interrupts, and how Linux loads executables.

A really nice delve into CPU inner workings, especially system calls and hardware interrupts are an interesting read.

A super in-depth and fairly personal guide to everything to get your freelance operation going.

I am amazed at the amount of concreteness and obvious labour poured into this for free.
If you have any inclination of freelancing - setting your own costs and choosing your own clients - this takes you through the billing, tools, clients, rates, tricks, and more.

It is strongly focused on web development but some parts can probably be adapted to other areas.

D programming language tutorial from the ground up.

Really extensive documentation and guided tour of the D language. From simple hello world to parallelism, concurrency, and manual memory management.

From a dude who knows how to explain. Aimed at mostly intermediate use (& a little advanced i suppose)

Amazing concise guide for simple IO stream explanation. Good as a refresher for whenever I have to work with them.

Short and simple video lessons that start from scratch. Tools and thoughts that might make your professional life more enjoyable.

• Tools for checking your python code (pylint, precommit, pyinstrument, ...)
• scikit-learn
• visualization
• cli tools like entr, makefiles, typer, rich, ...

Neat!

The full book online, and perhaps the best resource to learn Haskell.

If you know some programming but not functional or haskell programming, this should be the right resource.

Using altair to visualize data, a book by jjallaire. Nice explanations, starts from the basics.

Learn SQL. Interactive 'book', light-weight and intends to be the 'best place on the internet for learning SQL'.

Looks awesome to learn!

Use SQL queries to solve the murder mystery. Suitable for beginners or experienced SQL sleuths.

Lean SQL with a murder-mystery game. How cool!

Very nice list of bash-internal functionality. Mirrors the 'pure-sh-bible' by dylanaraps.