My family always used the dog carriers and/or dog treats to quiet our dogs, when I was younger.
If the dog barked more than it should, it was put in the carrier which was stored in a quiet room. Then the door was shut and he had to stay in there until he was quiet. When he was quiet for 5 minutes, he was let out.
Also, doggy treats. My sister carries some in her pocket, and when the dog is good, he gets a treat. When he's barking, he doesn't. So he knows that if he's barking for no reason, that he won't get a treat. He knows that if he's behaving, at times when he would typically bark (another animal in the area, the mail carrier, the tv, etc) he will. She just breaks little pieces of the treats up, so that she's not giving him too much in one day. That seemed to help her dog quiet down. She has a very small dog, and they're known to bark more frequently then the larger ones, or so I have heard.