A friend sent me a link to this amazing video. http://www.ted.com/talks/arthur_benjamin_does_mathemagic.html
I tried to figure out how to embed it so that you could watch it directly from this site, but couldn't, so just click on the link and it will take you directly to it.
I am so intrigued and astounded by the amazing capabilities of the brain! This man is faster even than the calculators in calculating square roots of huge numbers.