In an earlier post, United States Household Income Map, I had 2000 data by Census tract via Social Explorer. The Census just releases their 2006 American Community Survey with updated income data which is available using their thematic mapping tool. (Unfortunately the map is not available by county for all counties, so I am posting it by state). If you would like to drill down on the data go to US Census Thematic Map of Median Household Income.
[tags]income distribution, income map, Census, American Community Survey[/tags]