Codecademy provides free, interactive coding courses in 12 different programming languages, including Python, Java, SQL, C++, Swift, as well as HTML and CSS.
Coursera offers a wide collection of computing courses that are backed by accredited companies and U.S. universities, such as Google, IBM, Stanford University, and Princeton University.
edX is a platform developed by Harvard and MIT. It hosts university-level online courses in a variety of disciplines, with those relating to computer science being one of most popular.
Hackr.io aggregates high quality courses from many providers to make it easy to find the best courses. The site also makes it incredibly fun for users to learn how to code with a programming buddy.
W3Schools is a web developers site, with tutorials and references on web development languages such as HTML, CSS, JavaScript, jQuery, Java, C++, React, Node.js, and Bootstrap.
Khan Academy tackles computing by providing practice exercises, instructional videos, and a personalized learning dashboard that empowers learners to study at their own pace.