Sounds like your dog is a good watch dog. Are you sure you don't want her warning you when people come to the door? I'm not sure if you are aware or not, but sometimes thieves will knock on a door to see if anyone is home before breaking and entering. A dog barking is an excellent deterrent.
If she's carrying on 10 minutes after you open the door and let guests into the house, or barking and going crazy at any stranger who walks by that's one thing... but I'd never correct a dog for barking when people come to the door and knock. Think of your dog as an automated doorbell :)
Never trust a tall dwarf... he's lying about something.
I usually say, "Okay, Okay, Let's see what it is!" Then I open the door, but they have to be sitting at attention first. If they can't contain themselves, then they must go to their crates before I open the door. I always praise them for barking and then I ask them to "settle down" because "I'll take it from here."
I do the same thing if they start barking at the window. First, "Good dog. THANK YOU letting me know." then "okay, I'll take it from here."
A guard dog trainer told me that people ruin perfectly good watch dogs by yelling at them when they alert. He said that the owner is the alpha so that they should investigate the situation but that the dog should be praised for alerting to it.
This works for my dogs, but you have to be consistent.
Thanks for the answers, although the type of barking that I'm specifically talking about is stuff like when the pizza comes to the door... Tuna will NOT STOP barking, or get away from the door (we don't let her out the front door, for safety's sake) and if she's REALLY excited she'll do annoying stuff like licking the cap of the soda. We don't have a crate for her, but is there a way to let her know that all's OK? Jerry Lewis
If someone knocks on my door, the dogs go ballistic. When I get there I tell them it's ok, and besides one bitch, they all shut up and stand back. I want my dogs to bark, when they hear something. It can be tiresome in the summer time when the young kids are roaring around on trikes, or just walking around yelling, but I will never be caught unawares, anyway.