This graphic posted to Flickr by Eric Fischer maps Los Angeles County's racial and ethnic diversity, using data from the 2000 census. Each dot represents 25 people. Color code: red is white, blue is black, green is Asian, orange is Hispanic, gray is other. Fischer has done several U.S. cities and looks forward to plugging in fresher data from the 2010 census. Via the blog L.A. Taco.
Historical data: See how racial and ethnic distribution has changed in Los Angeles from 1940 through 2000 using census data, at Social Explorer.com.