Phil Plait is an astronomer, blogger, author, lecturer, and TV science documentary host. His blog, Bad Astronomy, is hosted by Slate Magazine, and his TV show, "Phil Plait's Bad Universe" aired on the Discovery Channel.
Phil started out as a professional astronomer, but has switched careers a half dozen times, from 1) astronomer to 2) public outreach guy for several NASA satellites to 3) author of two books ("Bad Astronomy" and "Death from the Skies!") to 4) professional blogger - his Bad Astronomy blog is one of the most popular science blogs in the world - to 5) professional skeptic to 6) public speaker and TV science documentary talking head guy.
"Blogger" is the one that's stuck, mostly because of the lack of a pants wearing requirement.
He's a huge and unabashed fanboy and geek, loving Doctor Who, Stargate, Star Trek, MST3K, and pretty much anything with spaceships and aliens, written or televised.