One of my favorite magazines, Good, recently posted a link to the new site This We Know, which compiles and synthesizes US government data. The site is still in its infancy, but it's already proving to be a great tool for looking up information such as unemployment rates and cancer rates per city. It's a little like a more comprehensive, at-your-fingertips Self guide for healthiest cities.
One data field that I found particularly compelling (and scary) was the pollution index. When I looked up my city, Berkeley, I found out that there are four factories within three miles of my house, emitting 1,273 pounds of pollution, which sounded like a lot until I compared those numbers to the nearby city of Mountain View, CA, which has two factories within a mile of the city, yet releases 781,441 pounds of pollutants!
You can also look up the most healthy and most toxic cities in the US, as well as statistics including the most nomadic cities and those with highest unemployment. This is all great data, especially if you're considering a move. Check out all of the statistics for your area here.