The Massachusetts Institute of Technology (MIT) OpenCourseWare program provides 2,000 online courses for free. Available departments include Architecture, Brain and Cognitive Sciences, Electrical Engineering and Computer Science, and more. Upgrading to full tuition costs about $41,000 more.

Also of note, The Open University, based in the United Kingdom, has 600 online courses for free. It's available to everyone. Choose from Arts and Humanities, Health and Social Care, Languages, Law, Math and Statistics, and more.