Zillow Labs has released the neighborhood boundaries of almost 7,000 US neighborhoods and 150 cites. The data is being shared under a Share-Alike, Attribution-Required Creative Commons license. On the detail page you’ll be able to find “zipped neighborhood boundary file for each state in the shapefile geographic format”.
This comes just a week after Urban Mapping released their free neighborhood API (Radar post). Suddenly the geo community has two neighborhood APIs to choose from. The reality is that they overlap in functionality (UM has more neighborhoods and is easy to use for neogeographers, while Zillow has released boundaries) and they will most likely be used together — after somebody does the work of syncing them.
(via GeoWanking via Spatially Adjusted)