I'm looking for resources for kids who enjoy very rapid and intense intellectual stimulation.

Of particular interest to my own DS8 were Vi Hart's math videos:

https://www.youtube.com/user/Vihart

These are passionate, fast-paced and full of thought-provoking material.

What's the best you've seen?

DS10 (DYS, homeschooled)
DD8 (DYS, homeschooled)