Challenges / Competitions
- Daily programming task ; starts simple and moves to complex ; language agnostic;
- Google Code Jam, yearly programming challenge, difficult to very difficult;
- Leetcode ; mostly interivew related programming challenges;
- Project Euler, more mathematical but many problems and different difficulty level
Tutorial (Programming)
- Khan Academy - JS, HTML/CSS, Advanced JS, SQL; starts very basic, a complete introduction and mostly interactive
- How to think like a Computer Scientist - Introduction to programming and Python - Completely interactive
- Programming Python (nice and concise) (incl. videos in the side links)