Zoning - New York City Department of City Planning
This website was extremely useful in helping me understand the potential uses of a large parking garage just behind a building that a client wanted to buy in. We actually had an accepted offer, but this garage was nagging at him and we really didn't have any concrete answers regarding the possibility of it being torn down and a larger structure being developed.
I called the Department of City Planning and left my contact info along with the lot/block # of the building in question. Of course I was very skeptical that I would get a call back, but a few hours later a very helpful woman called me with all the information I had requested. She even answered my question about a "HAZMAT" designation the building in question had; quite common and not really an impediment to build on the lot (in this case old buried gas tanks are on the site).
Well I hope you find this useful, along with sites like UrbanDigs, StreetEasy and ACRIS you have more tools than ever to help you make a smart, informed decision about your next apartment purchase.