Although the web allows for communication on a global scale, I love the local resources it makes available just as much. New York Songlines is a fascinating site with annotated maps of New York City maintained by Jim Naureckas. Simply designed, each map is a linear representation of a single street (here's Bleecker Street, for example), with links available to switch to cross streets (here's where Bleecker crosses MacDougal). The maps are annotated with information about who lived where and when, contemporary commerce, location info for notable movies, and architectural history.
Some examples from the map for MacDougal Street:
93: Was the San Remo, famous bohemian hangout of Burroughs, Miles Davis, Tennessee Williams, James Agee, Jackson Pollock, W.H. Auden, Frank O'Hara, Village character Maxwell Bodenheim, photographer Weegee, etc. Gore Vidal once picked up Jack Kerouac here. Lost popularity because the bartenders beat up the customers once too often.
121: Authentically charming since 1927. Featured in Godfather II, Serpico, Next Stop Greenwich Village and the original Shaft. JFK gave a speech out front in 1959.
130-132: Louisa May Alcott wrote Little Women in this 1852 house.