I'm very interested in the 'free courses' trend and have participated in several MOOCs now. I'm writing this post mainly for myself to keep overview of MOOC providers. Once in a while someone sends me a link to another free course and I'm surprised that I don't know the provider.
This overview is just a start, I'm sure there are many more providers! I'll try to update with more information, or leave a comment with providers that I should add.
Coursera: many courses in different languages. By far the biggest in number of courses. I've done several, mainly from US universities (more are joining, from all over the world). New are specializations, verified certificates and own pace courses. Free to enter, however you pay for verified certificates. To get a certificate, usually the requirements are a mix of quizes, assignments, peer review, forum participation (the verified certificate requires more).
edX: courses from some of the well-known universities like MIT and Harvard (that founded this platform). TU Delft is one of the partners. Topics include business, chemistry, economics, philosophy.
Future Learn: all courses in English, delivered by mainly British universities. Language courses are interesting (Dutch for beginners). Categories: Business & Management, Creative Arts & Media, Health & Psychology, History, Language & Culture, Law, Literature, Nature & Environment, Online & Digital, Politics & The Modern World, Science Math & Technology, Sport & Leisure, Teaching & Studying.
Class Central: seems to give an overview of MOOC courses delivered by Coursera, edX and so on (also commercial partners). Good starting point to find a course on a certain topic, if you don't care who provides it.
NovoED: with emphasis on 'social' (social learning, social impact, social entrepreneurship etc). This is where I'm doing a Human Centered Design course right now. It requires more practical assignments, less videos (compared to Coursera). Categories: Humanities, Social impact, Education, Design & Creativity. Most are for free, some courses ask a small entry fee.
Open2Study: Australian provider, from the Australian Open University. I've done two courses here, found them less demanding than the Coursera courses, both in time and finishing requirements. My main struggle was the Australian accent of the instructors! Categories: Engineering, Business & Management, Health & Medicine, Education & Teaching