Not a channel per se, but you can find very interesting videos on the history of mathematics by the open university. They are rather old and the use of artifical fog in the beginning is a little bit annoying, but Jermey Gray is very competent (albeit touching the Newton Manuscript which at the time was not as frowned upon as it is today).
A few links:
In case you happen to speak Hebrew, I can also recommend the videos by the Open University by Leo Corry:
I really enjoyed the Yale lecture course for a broad overview of the early middle ages.
/r/TheGreatWarChannel Is doing episodes weekly following what happened in WW1 100 years prior that week. And Summaries of every 6 months.
Along with many special episodes covering topics related to WW1. Covering topics subjects asked by many viewers such as America before joining the war and Poland's Struggle for Independence During WW1
They also have a whole series of Who did what videos covering people from regular soldiers that would later become famous like Hitler, Tolkien and Auto Dix. And leaders such as Conrad von hotsendorf, Kaiser Wilhelm, von Lettow-Vorbeck The Red Baron and Mustafa Kemal Atatürk
They also do some more lighthearted fare such as The Top 10 Moustaches of World War 1
For some lighter entertainment/learning, I personally love both Extra Credits' "Extra History" episodes (the rest is great if you are into game design/theoretical stuff about video games) and the Crash Course history series. Both are not that in-depth and often oversimplify things quite a bit, but they are very entertaining to watch and good for a rough overview. Both also try to slide away from the usual Eurocentric history stuff quite a bit, which is refreshing.
Probably the best series you will ever find on "World History". It might come off as a bit advanced; but if you know your history well enough, you simply will not learn from a better soure anywhere.
Richard Bulliet is not only professor emeritus (now retired), but someone who has written his own world history textbook.
You can find the series here. He also has it on iTunes, along with a couple other lecture series on History of Iran and Modern Middle Eastern history.