The days of everyone in a neighborhood knowing and helping each other are over. Nowadays, especially in the suburbs, it's common for neighbors living right next to each other to not know each other's names. Nextdoor is a free iOS app that's attempting to turn this sad state of affairs around by using an easy-to-use social network to chat with neighbors.
I've been using Nextdoor for about six months on my iPhone and have found it to be extremely useful to find out what's going on the neighborhood where I've lived for 33 years. You load the app, let it determine where you live, and then choose the neighborhoods besides your own that you wish to get information about. If there are neighbors near you who isn't using the app, you can request to have up to 50 postcards sent out asking neighbors to sign up the free service.
Nextdoor is probably one of the most useful social networks I've seen. People ask questions about construction in the area (that's the way that I found out a huge indoor recreation facility is going in about a mile from where I live), post about lost or found cats, dogs and iguanas (yes, the latter happened last week!), get clarification about local regulations, and give away or sell excess items.
The latter is much more useful than Facebook, for example. Here, you know that a person listing an item for pickup or sale lives very close to you instead of on the other side of a metropolitan area. Neighbors will often give used items away for free and just say "pick it up at XYZ", and before you know it the items are gone. I've seen neighborhood kids get jobs babysitting or doing lawn work, and questions on just about any local topic are answered quickly.
Our local sheriff's department has a presence on Nextdoor and they inform the local citizens about crime alerts, things like National Prescription Drug Take-Back Day, road closures or hazardous conditions, and so on. Our local Metro District (we're an unincorporated community of about 100,000 people) also has a person who keeps the neighbors up to date on local events, rules, etc...
There are ads, but they're nicely placed in the middle of the feed and in most cases, quite topical.
Nextdoor is an amazing way to get to know more of your neighbors in the nameless, faceless suburbs and urban areas, and I highly recommend it.