GIS at Grinnell - Details tools, support, training and data available at Grinnell College, and includes a showcase of class projects with GIS.
Iowa Geographic Information Clearinghouse Metadata Explorer under Resources (Click on Data) - a comprehensive way to collect data about specific areas of the state or the whole state.
American Factfinder: Thematic maps page- A direct link to the thematic maps page of the Census. A little difficult to navigate, but provides access to graded color maps of a number of data tables from the 2000 and 1990 Census.
Other links of interest:
Edward Tufte's Home Page - Featuring the work of Edward Tufte and Graphic Press.
Examples of Bad Graphs - from C. J. Schwarz, Department of Statistics and Mathematics, Simon Fraser University
NITLE (National Institute for Technology and Liberal Education GeoSpatial Studies Initiative - includes information on ArcGIS in the liberal arts curriculum and links to GIS-related blogs.