The Digital Atlas of New York City, put together by William A. Bowen of California State University, Northridge, has a bunch of interesting maps of the Big Whatsit. This, for instance, is from the map showing the distribution of the black population in NYC:
(By the way, does that pattern look familiar?) The atlas also has maps showing income, education, and ancestry - you can see which parts of the city Dutch or Dominicans have settled in, for instance. The only drawback is that it's a bit dated. It's a problem for demographic maps for the US in 2009: the decennial census is a year away, so everything's based on data that's 9 years old.
Ah, and just now I notice that Bowen has similar atlases of Seattle, DC, Boston, Chicago, Honolulu, LA, San Francisco, San Diego, and Sacramento, as well. And also a bunch of other maps. So there you go.