Become a professional software developer

Free online courses

CS50: Computer Science Courses from Harvard: Harvard's famous introductory computer science course.

Think Java: How to Think Like a Computer Scientist: Hands-on introduction to Java programming and computer science.
Eloquent JavaScript: A thorough guide to Javascript programming.
High Performance Browser Networking: An excellent, in-depth guide to browser networking.
Structure and Interpretation of Computer Programs: A difficult book on the fundamentals of computer programming and programming languages.
A Course in Machine Learning: Introduction to most major aspects of machine learning.