Eric Fisher is at it again - this time he's made some maps to illustrate ethnic diversity in 40 U.S. cities. Here's Seattle:
image from Eric Fisher; used under Creative commons license
Each dot represents 25 people - Red is White, Blue is Black, Green is Asian, and Orange is Hispanic. The categories themselves come from the census, because that's the best available data. If you know Seattle reasonably well, there won't be any big surprises in this, but it's a very effective way to visualise the data and it can be interesting comparing other cities.