Developers are very good advertisers. For those developments on the outskirts of town there are usually signs along the highway near their new community. Many developers have great websites with floor plans, prices, and pictures of their houses. Search on “city + state + new homes” to get websites for developers in that city.
I have found that one of the best places to see announcements for new developments is in the newspaper. Most newspapers have a real estate section that is devoted to not only the buying and selling of existing homes, but also to the ads from developers. The local newspaper and the closest major newspaper are really full of information for the home buyer, from what is for sale to local mortgage rates.
Another way is in those real estate ad magazines that are offered free at the entrance of most grocery stores. These publications contain a wealth of information on what is for sale and who is building in which area. As real estate has become a popular investment, these free publications are showing up right on the street in their own metal distribution containers.