Crash Course is part of the Internet force that is the Vlog Brothers; aka nerdfighteria, aka, Hank and John Green. Their videos feature some of the best video production on YouTube.
World History
This is the first of two Crash Course World History series. The above-mentioned John Green takes you from Agriculture to Globalization in 42 videos. I never fail to be impressed by the polish on these fast-paced, richly illustrated videos. I wish I had had videos like this when I was in school.
World History 2
If you loved that one then here's the World History 2 playlist. It explores more general issues and questions how we think about history (and the present), how the past led to today and whether we should keep things that way.
Literature
Next we have less history but plenty of John Green. I really enjoy Green's perspectives on literary classics and writing tools in general.
Astronomy
No more John Green but that's okay because Phil Plait is awesome and they're in the Crash Course Style that you hopefully love by now. Plait gives you the tools to enjoy the sky and then shows you what to use those tools for. I desperately want some binoculars now.
Chemistry
My last Crash Course playlist (but not the last one there is). This time it's John Green's brother, Hank. Hank, like his brother, manages to turn overwhelming concepts into manageable pieces even when those pieces are the building blocks of the entire universe.
Hank makes me laugh out loud more than anyone else at Crash Course and that's saying a lot. I never thought I would love chemistry but the playlist below changed my mind. Few things make you look at the entire universe differently and this is one of them.