Regardless of one's opinion of Mayor Bloomberg, his administration has done an incredible job of putting public data online in an accessible format. If you are looking for property data, for instance, this site can guide you to everything from deeds and mortgages to liens to violations to maps.
This past week, the City's Department of Information Technology & Telecommunications (DoITT) launched NYCityMap. If you want to read about all of the cool features of this map (including political boundaries and property info), check out the user guide. But, I would have to agree with this Times editorial: the most amazing part is the zoomable map of the City in 1924.
...click on the camera at the top of the page and move the slider beneath it back to 1924. The interactive city of 2010 fades away to reveal an aerial view of the five boroughs assembled from photographs that have been digitally stitched together.The effect is not as simple as it sounds. The old city doesn’t merely replace the new one. It seems to resurface from within it.Of course, what readers of this blog will really want to do is to check out the Bronx 86 years ago. A new Yankee Stadium is just across from the Polo Grounds... intact neighborhoods sit where the Cross Bronx Expressway would eventually tear them apart... Fordham Hospital sits at the intersection of Southern Boulevard, though most of the University's main buildings are not yet built.... the Keeper's House sits across from the Oval -- still operating as a reservoir! Lehman College, and much of the Concourse, for that matter, are yet to be built. I noticed that my street, Rochambeau, ended at 206th Street and the whole block down to Bainbridge looks like a grand estate.
Below are a couple of screen shots of Norwood, Fordham and Bedford Park. But of course you will want to spend some time perusing various neighborhoods on your own. Feel free to post interesting things you discover about your neighborhood in the comments section!