TheKidShouldSeeThis is a fantastic website that curates all kinds of videos that are fascinating for children of all ages! These videos, from all different sources and about all different topics, are short, delightful, and renew a sense of wonder in both children in adults. Give it a try!
Crash Course Kids This YouTube channel from the creators of Crash Course presents a collection of educational animated science videos (the website hopes to add more topics later.) This is an excellent resource, and very easy to use!
NASA has an amazing website for young space cadets! The interface is amazing, and there is a special section for youngsters. You can choose from three TV channels and watch launches live, ISS live feed, or announcements. See what is happening on Mars, in deep space, or right here on Earth. Awesome.