I found http://www.oldsf.org a few months ago as I was trawling through old photographs to identify any old shots of the Haight area in San Francisco for a house history I was working on. The creators of the site assigned a longitude and latitude to many of the images in the fantastic digitized collection available at San Francisco Public Library’s Historical Center. They were then able to plot the photographs on a map of the city, making a search by specific location much more accurate. They give full credit for the digitized photos to the library. The staff at the Historical Center have added OldSf.org as a link on their web pages so they are clearly impressed with it too.