We had an "official" one for several years. I was captain for 3 yrs. during that time, we established an email/phone list for our block. It is very easy to alert everyone with an email if something needs to be imparted. We also invite our police officers, postal carrier and fire dept. to stop by at our annual potluck.

Had a neighborhood that didn't have one for 1st 15 years but created one. The neighborhood and actually improved in attitude and appearance.

Our neighborhood is great in terms of notification. Everybody within a couple of blocks are on an email thread, notified of any misdeeds in our 'hood. It helps everybody remain vigilant for the common good. We have had, as pikespeak mentions, input from the local PD in terms of the best means to deal with criminal acts which are trending in the area.

We have "neighborhoods" defined by my city, throughout the city. I started a neighborhood watch 8 years ago after a rash of breaking-and-enterings when neighbors were already mobilizing and trying to figure out what to do about them. I was advised by our PD to "just start SOMETHING" and let it evolve. We started with block captains who spread the word, collected contact info for neighbors, and were point people for communication. Very dependent on people being home and willing to be block captains. We have moved to a system where we use a listserve "group" hosted by Yahoo where any member can post something and it instantly gets sent to everyone in the group. After years of promoting it, we now have 435 members, loosely confined to our neighborhood boundaries as established by the city. I have direct contact with the second in command in our police district, so information flows accurately and (fairly) quickly when needed, both ways. I have recently been asked by the PD to serve as a consultant for others looking to start a program in their neighborhood. I believe the reason we have had so much success is because we don't limit our posts to crime-only. It functions as a neighborhood bulletin board for all sorts of things, so we keep up the chatter and stay connected about positive things, so that when something crime-related occurs, we're not strangers, and we remember to alert each other about even small things.

Like dogmycopilot, our neighborhood association has had up and down cycles in the past, but now it's stronger than ever.....we have a neighborhood association FB page that has helped tremendously in pulling together neighborhood residents in everything from crime alerts to lost pets or strays to social functions and activities to needs and opportunities to help each other out.