Tutorials for learning Arduino, through the Arduino Project Hub, or through built-in examples that you can run in the Arduino IDE.

Raspberry Pi official courses that walk students through basic to complex projects ranging form physical building, to coding robots, to web development.

Instructables contains hundreds of step-by-step project guides for various circuitry projects, including Arduino, Raspberry Pi, sewable circuits, paper circuits, and more.

A wide range of guides covering the basics of electronics.