The Racial Dot Map shows at the level of one dot per person the racial makeup of every census block in the US. This map was created by Dustin Cable of the Cooper Center. Below is a zoom on Minneapolis.
“While Minneapolis and St. Paul may appear purple and racially integrated when zoomed out at the state level, a closer look reveals a greater degree of segregation between different neighborhoods in both cities. While some areas remain relatively integrated, there are clear delineations between Asian, black, and white neighborhoods.”

Dustin Cable’s Racial Dot Map
This is great, but I wish you could zoom in one more level. Also it does some strange generalization thing at larger scales that seem to show lots of (white) people living in mountain ranges.
For a similar (and seemingly more high fidelity) racial dot map project, check out these mesmerizing race dot maps of different US metro areas (scale is one dot per 500 people): http://www.flickr.com/photos/walkingsf/sets/72157626354149574/detail/
Looking at these maps is something everyone should be doing on a regular basis. It’s all to easy to remain isolated in one’s enclave.
The NYT also has a similar visualization. A couple differences are that it groups by tract not block, it has the number of people per dot decrease as you zoom in, and also has a mouseover so you can look at the numbers, including change since 2000. http://projects.nytimes.com/census/2010/map, then View More Maps, and pick Racial/Ethnic Distribution.
Regarding your first point, it seems like a technical issue related to the size of the dots–they don’t seem to get proportionally bigger as you zoom in, so it looks more dense as you zoom out?
About your last point, I think it’d be best for people to get out and visit places they don’t normally go, not just look at the maps. Odds are, they’d notice the same demographics, along with lots of other interesting things!
Not sure if you can toggle on/off individual race/ethnicities – it’d be interesting to see the distribution of an individual group with others turned off. Just as floodplains and open space are scarce of population, I’m sure certain groups are just as scarce in various parts of the metro.
Good Point Tim.
These maps really are amazing, but I also wonder about the color theory behind the digital choices. For example, white people are blue and I wonder how strongly the presence of different minority groups would read if the white people were yellow or orange.
Don’t really know, but I know how important those kind of Infographic kinds of things can be.