I vote for Advantage, manufactured by Bayer. I LOVE Advantage, we used it inside the vet clinic. We never used anything else in the boarding kennel at the vet clinic. People would bring animals in to board and they would be covered with fleas. We would start with a Capstar, if it was REALLY REALLY bad, but we always used Advantage. It's awesome.
I have stopped using Frontline, it just didn't seem to work very well. I saw a drop in flea populations, but they were still around.
Now with Advantage, I see maybe one or two fleas, but I know they will die quickly after biting the dogs. But, this is what I use on my dogs, all three come into the house.
-Kim