Awesome Resources
Great resources to do stuff!
Markdown
commonmark a useful basic resource on the Markdown syntax
Version Control
git - the simple guide very simple but complete git guide, no deep stuff The Least You Need to Know About GitHub Pages blazing-focused github pages learning guide
Microcontrollers & SBC
The Raspberry Pi guide for scientists and everyone else nice, to-the-point guide on using the Raspberry Pi A Beginner’s Guide to the ESP8266 quick introduction to ESP8266 programming with examples
Mathematics
Complex Analysis interactive web book an amazing interactive online book to learn complex analysis