Image Gate is pretty damn cool. I especially like the photos showing the construction of the Holland Tunnel. The pictures aren’t all NYC-specific, though. There are collections of cigarette cards, portraits of Native Americans, and maps of the mid-Atlantic region, among other collections.
From the Image Gate Web site:
Image Gate is The New York Public Library’s first full working version of its new digital image database. Image Gate provides free and open access to thousands of The New York Public Library’s digitized images, taken from the Research Libraries’ collections. At its inception, the Image Gate database contains approximately 80,000 images spanning a wide range of subjects. This number will grow as The Library digitizes more images; this phased rollout will end in 2004, when the site will include more than 600,000 images. Image Gate demonstrates the rich potential for discovery in The Library’s vast international collections of prints, drawings, photographs, illuminated manuscripts, rare books, maps, popular graphics and printed ephemera.