If you're not familiar with the concept of Youtube channels as a way of filtering for high quality educational video online, then this web page is a good place to start. It suggests ten channels to subscribe to, including some well-known ones, such as Khan Academy and TED talks.
As well there are some more 'niche' channels such as Expert Village ('how to' videos), Nobelprize.org (current feature video a Nobel Peace Prize lecture by the Myanmar activist Aung San Suu Kyi), and Edutopia (what works in education).
NOTE: to go to the featured channel on the web page, click on the text link NOT the banner logo for each channel.
My rating: 9/10