Sentdex has some excellent videos on python, surprised nobody mentioned him yet.
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.
Just going to add Clickspring to the machining category. Content doesn't come up as often, and there can be an immediate reaction of "wow, that's above my pay grade" because of the things he's making and the video production, but in the end Chris is a hobbyist using hobbyist tools and doing a lot of hand work, all with good explanations.
> Maching/shop: This old tony and mrpete222. Ave is entertaining but not too educational
Please also check out Abom79, Keith Fenner / Turn Wright Machine Works, Keith Rucker / vintagemachinery.org, Tom Lipton / oxtoolco, Stefan Gotteswinter, and ROBRENZ (this guy _really_ knows what he is talking about)!
Ave is extremely entertaining, but I think he is highly educational. He imparts a lot of pratical knowledge, that you won't find elsewhere. Knowledge about molds and manufacturing.
As much as I want to like sentdex he's a bit lacking in depth and experience. For security you forgot Gynvael if you have the time for a 2 hour livestream vod.
I’d throw in Periodic Videos for chemistry, brought to you from the same guy who does Numberphile. It’s just a pleasure to watch, even if you already know the material. MinutePhysics is also a lot of fun as a teaching aid, or entertainment.
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.