You can watch the first episode (which premieres this coming Sunday) for free on line courtesy of Showtime. You'll be promtped for the password which is sneak peek. Michael C. Hall stars as a Miami cop who moonlights as a serial killer, taking out criminals in his off hours. Dexter is based on the novel, Darkly Dreaming Dexter, by Jeff Lindsay.
I am waiting for Sunday myself.

http://www.sho.com/site/dexter/sneakpeek/home.do