Currently I am watching Daniel Shiffman (example : https://www.youtube.com/watch?v=_p5IH0L63wo) and I really like his enthusiasm. I've watched a whole bunch of high production, paid courses (udemy, udacity etc) and somehow Shiffman's free videos are more fun to watch and learn.
Any other teachers you like? Doesn't need to be math or computers, other subjects welcome too
general engineering/science: Applied science is just so so good
Chemistry: NurdRage and Nile red are both good, although I prefer NurdRage.
Electronics: Mike's electric stuff, Mr Carlson's Lab,and bigclive.
Math: Can't beat 3blue1brown, although numberphile has some good content as well.
Maching/shop: This old tony and mrpete222. Ave is entertaining but not too educational.
Comp Sci: sentdex (python) and liveoverflow (security/Rev eng).
Most of these aren't courses, although they are all educational. For instance, applied science isn't trying to teach anything, he's just presenting his projects. But unless you are a true rennisance person I guarantee you will learn something from every video.
Edit: forgot to mention, check out speeches from conferences like cppcon and defcon, excellent sources that are sometimes easy to miss.