Partnering with world-famous universities, including Harvard and MIT, edX has around 2,500 courses to choose from. It focuses primarily on the humanities and natural sciences, so if you’re looking to broaden your understanding of topics in these areas, it’s a great place to start. Languages and computer science, in particular, are among the most popular subjects on edX. While most edX courses are free, there are some professional courses that will come at an additional cost, so make sure you know exactly what you’re signing up for before you commit yourself to anything.