Arthur Benjamin

I read this guy's book a couple of years ago and was impressed. I even taught myself how to square any two digit number my head. But in person, he impresses even more: just how quickly he does it is amazing (even when I was doing it a lot, it still took me several seconds to do a two digit number).



via Greg Laden.

As a bonus, here's a talk by Jared Diamond on why societies collapse:



Via Ted.