As you walk through the streets of your city, you might orient yourself by intersection, neighborhood, or the presence of your favorite coffee shop. This interactive map of London, however, lets you view the city a different way: by concentrations of Johnsons, Bennetts, and Patels.
James Cheshire, a lecturer at University College London's Centre for Advanced Spatial Analysis, created this map based on the 2001 Electoral Roll. The more frequently the name appears in a geographic unit, the larger it appears on the map, and the names are color-coded based on the origin of the surname (though not necessarily the origin of the persons bearing said surname). You can zoom in and out, poke around the city, and play with name popularity with the scroll bar to get an unusual view of London and its various neighborhoods.
Cheshire details his process on his blog, Spatial Analysis.