MOOCs

I'm generally curious, and have taken several online courses in the past. I'll list most of them here.

Obviously, despite the platforms' claims, these are very rarely at the level of a university course. They are usually bite-sized (doable in a week or two, with an hour of daily work at most), and the lack of skin in the game (in the free courses) doesn't help to dive in as deeply as one would in a university setting.
Above all, of course, it lacks all of the interesting people around, both colleagues and students, and the extra work one puts in because of them (as I said, skin in the game), as well as the serendipity and little personal discoveries that only happen when you're knee-deep in something for months or years at a time.

That said, they can useful for a structured overview of a subject, and I'm sure MOOCs can and will improve with time.

Courses in bold were my favourites, whether because they were demanding and in-depth, or simply because they were surprising and generally well done.

Certified means I've gone through the hoops (usually exercises and exams) to get a certificate. Audited means I didn't complete the exams or exercises (out of laziness, or because they were locked in the free setting).

Certified

Audited