Phil Plait
Science evangelist in Virginia, United States
I'm an astronomer, author, scifi dork, TV documentary talking head, and all around science enthusiast. I write the (independent) Bad Astronomy Newsletter.
I've given public talks on science internationally, including two TEDxBoulder talks that were picked up for the main TED page. I have talks on astronomy, space, scifi... and I can create new ones to fit your needs: My profile at Samara Lectures.