I thought you might be interested::
The city of New York owns thousands of slivers of unused land, and
about a year ago, a group of Brooklyn gardeners had an idea: identify
all the vacant lots in the borough, then help neighborhood residents
take them over. They built an online map, then a mobile app, with
information about the plots, including the names and phone numbers of
the agencies that owned them. They called themselves 596 Acres, after
the total area of unused public land in Brooklyn, according to city
data...
More: http://www.nytimes.com/2012/04/29/nyregion/a-plan-to-turn-brooklyns-unused-acres-green.html?src=recg