Online mapping pioneer MapQuest just launched a new local site to explore 50,000 U.S. neighborhoods. MQVibe uses the MapQuest API to display neighborhood shapes and highlighted places. The MQVibe API, while not officially launched, is used by the site itself and appears available externally.
MapQuest built its service on top of at least two of its own APIs. The obvious one is its flagship mapping API, used to display the locations. The company has a few neat features. For one, the city's neighborhood boundaries are displayed on the map, shaded based on their "Vibe Score." Also, the top places in a neighborhood are shown as larger markers than second tier places.
The not so obvious API is the yet-unlaunched MQVibe API. The API isn't documented, but MapQuest says it intends to make it available in the future. However, it appears that the API is available already and used by the app itself. For example, here is a bounding box search for Salem, Oregon. The API returns JSON data and supports JSONP.
Since the MQVibe site uses this API, the MQVibe API also provides the shapes of the neighborhoods in the city. For each neighborhood, you also have access to its Vibe Score and the several factors that make up the score: edginess, walkability, national chains, going out, "residentiality" and popularity.
MQVibe will be incorporated into the main MapQuest site, likely also using the MQVibe API. The company's vision is to include MQVibe results along user's routes.
MQVibe has a place scoring feature, which will likely become especially important when the API is officially released. Users can contribute to the places that MapQuest highlights by voting places up or down. Though it's unclear whether this is currently in the API, I'd expect voting will be part of the upcoming iPhone app. And that means at least the app's private API will be able to accept votes, so I hope that will make its way into the official MQVibe API.