I’ve been using coursera since it first rolled out, and before that (and still do) took many online classes on youtube.
Coursera has a nice interface, and many surprisingly interesting topics that I otherwise would not have sought out. I tend to subscribe to many, drop about 90%, but 10% will follow through. My favorites tend to be engaging professors with high production quality.
The thing I like about youtube is the classes are from like 5 to 10 years ago, so you can buy the textbook on half.com for about a dollar. I liked it for the science stuff (bio, chem, anatomy) but there is a really good one on the history of the new testament, and one on the history of infectious diseases.
As for coursera, my favorites that caught me by surprise were one on dinosaurs, one on the US food system, astronomy, and the history of the slave south.
Many are tech classes, and should appeal to me (I am a healthcare data analyst) but to me most of it is not real world applicable (like most of the computer classes I took as an undergrad)