Ork Posters! may have been first to the punch with their City Neighborhood Posters (which I absolutely love, by the way), but the awe-inspiring detail in the Typographic Maps by Axis Maps is certainly worth a look as well. The maps accurately depict the streets and highways, parks, neighborhoods, coastlines, and physical features of the city using nothing but type. Every single piece of type was manually placed, a process that took hundreds of hours to complete for each map.
Poster-sized prints of Chicago (black & white or full color) and Boston (full color) are available for $30 on the Axis Maps site.