Forbes Magazine has created a fascinating interactive map that allows you to select any county in the United States and track in- and outbound migration patterns based on a compilation of 2008 IRS data sets. You can access the map here.
Here’s the map for Dane County where I live, indicating significant migration all over the country:
I selected a couple of other WI counties and found the migratory level and locations to be significantly different. For example here is Fond du Lac county, with migration to the sunbelt AZ.