Since you already seem to be up all night, look up local noise and nuisance ordinances.
Call your local PD in the morning and lodge a complaint. They'll probably go to the house and contact the owner. Hopefully a visit from law enforcement will be a wakeup call to their inconsideration.
If the dog keeps barking at unreasonable hours, call the police DURING those unreasonable hours. They'll be miffed having to send out a car and will be a little more forceful with the owners, who themselves will have to wake up to the cops at their door. Maybe having their beauty sleep interrupted because of a barking dog will give them a little perspective.
Repeat the late-night complaints as necessary, someone will eventually get a clue.
Also, tape-record the barking and document, document, document!
Confronting the owners is really not a good idea, especially if you do not know them. They obviously don't care enough about their neighborhood to keep their dog quiet, so a confrontation would probably go down hill very quickly and as the one who started the confrontation will probably be on the wrong side of the law.