First try talking calmly and respectfully to your neighbor about the barking. If you're not on friendly terms, write a friendly note and leave it at their door. You can suggest that you would be willing to purchase an anti-bark collar if it's agreeable to them. If all else fails, there's usually an ordinance against dogs barking after a certain hour. You can contact the proper authorities anonymously and ask them to contact your neighbor. Don't discuss the barking with other neighbors to avoid more problems.