I found this link interesting: you are where you live.
Basically, you give it your zipcode, and it describes the people who live your area. For example, using my zipcode I get these results from the PRIZM system:
Winner’s Circle
Executive Suites
Young Influentials
Suburban Sprawl
Towns & Gowns
And I get these results from the Microvision 450 data set:
A Good Step Forward
University USA
Middle Years
Upper Crust
Urban Up And Comers
Pretty interesting stuff (and pretty accurate based on my impressions of the community).