Many communities have their own local register of historic places, and some even have markers to show these places off. New Haven is fortunate to have The New Haven Preservation Trust that is responsible for placing bronze plaques on designated buildings. The design is fairly straightforward and a simple elliptical shape with a symbol in the center and the text "A New Haven Landmark" above in larger letters, and "The New Haven Preservation Trust" below in smaller letters. There are two bulls eye shaped mounts where the plaque is affixed to the building.
Unfortunately when visiting the NHPT website there is no easily accessible information about the marker program. Reading into it somewhat, it could be this program is either not advertised or is being phased out. Some communities have found Wikipedia to be an effective and free tool to organize data about historic properties designated at the local and federal levels. One such example is the List of Town of Oyster Bay Landmarks.
The Historic New Haven Digital Collection through Yale University, provides a unique assortment of images, maps and data sorted by neighborhood. This has some interesting potential to help make research materials broadly available. Combining materials from this collection with information about landmarked properties might have some real potential.
Lastly, while identification plaques are helpful, increasingly people are looking for more interpretive information. Having a number keyed to each location that corresponds with a website, audio tour, printed guide, cell phone tour, or some combination of the above would help to make more interpretive material more available. Doing so would help to create a stronger connection between the public and landmark buildings that groups like the New Haven Preservation Trust are seeking to protect.