transparent NYC   (link)

http://skyscraper.org/timeformations/transparent.html
a bunch of overlays of new york city: historic districts, commercial zones, urban renewal, highways, subways, monuments & parks, rails, piers & bridges, elevated trains, 1811 grid, grids, landfill farms, british colonization, dutch settlement, topography, (new?) office buildings for different date ranges

sources include New York City Planning, MTA (Metropolitan Transport Authority, i assume), Sanborn, Department of Docks Map NYPL, Rapid Transit Map NYPL, Commissioner's Plan 1811 NYPL, Map of New York City 1805 NYPL, Viele Sanitary 1870 NYPL, Map of Farms 1807 Municipal Archives, British Army Headquarters Map 1780 NYPL, Castello Map 1660 NYPL

Also see Brian McGrath's Transparent Cities