The speculation on who is the last Cylon on Battlestar Galactica is building up. I even touched on the topic, and linked to Peter David's speculations. Now even TV Squad is getting into the act. One litmus test I apply to anyone's guess: when one of the Cylon models D'anna (Lucy Lawless) saw the last Cylon, she said "Oh my God, I had no idea... forgive me..." I would see if that guess would fit with that scene.
After reading the TV Squad article and comments, I have my guesses that I'd rather not say right now, but one I will say isn't is Starbuck. Usually on these types of shows where you guess whodunnit or whoisit, the one that the show points to and has obvious clues, isn't. Of course the show could do a double-fake and make it her. But I think the backlash would cause the ratings to drop faster than you can say "worst episode ever".