Illinois Natural Resources Geospatial Data Clearinghouse

From my hometown Urbana, vector and raster data for all the world!

"Access Illinois GIS data sets and documentation (metadata) for ArcIMS Interactive Map Services, USGS digital topographic maps, aerial photography, orthoimagery, orthophotography, geology, land use, natural resources, and infrastructure. Illinois data sets and map data layers are available for download free of charge."