There was a great article in the New York Times last Friday about a group in the Fort Greene neighborhood called Brooklyn Cohousing.  They were able to purchase an unbuilt condo development based on a rehabbed church property with a 7500sf central courtyard. 
They intend to turn it into a green, sustainable community with individual, fully equipped apartments as well as common space where members of the community can gather to share meals, gardening, and childcare. 
It looks like a great project and they are actually on track to move in early 2010!