How about laughing? Works for me but my dogs have not been as bad. Mostly mine have reached an age, around one year old, where they somehow got it into their heads that it was their job to guard our property. Or to notify of approaching strangers. My tack is to show them they are wrong, it's MY job.
Laughing is really only one thing I do. Laughing shows them they are wrong and I am not worried about whatever the situation is. After all, if I felt threatened would I laugh? No. So I laugh, sort of mean sometimes, like the school bully who laughed when you slipped and fell on ice. "Ho, ho, ho, you big dummy, that's nothing to bark at. You are wrong, You made a mistake." Works for barking at the door bell type situations.
I do some obedience. SIT, DOWN, STAND. This is distracting and reinforces my control of dog as well as situation.
With one young dog who began to advance barking at strangers we met in the bush I did the obedience but also discovered that my greeting the stranger in a happy, familiar way did loads to reassure the dog as well. " Hi there, great to see you, what a beautiful day. How are you anyway, it's been ages." If they were strangers I'd get some funny looks but it tricked the dog into thinking, hey, Mom knows them, Mom is being friendly and happy, gee, it must be all right, I won't bark. It worked every time till she just stopped and left it all up to me.
Another trick I really like is Leslie McVitt's and for that I will ask you to check out this site. It's been great for this and some other behaviour I didn't like. http://www.dogwise.com/itemdetails.cfm?ID=dtb943