Social explorer is a site that lets you create a variety of demographic maps and save them as a slide show.

The National Atlas which also allows you download data as ArcGIS shapefiles.

Both the Map libraries at Stanford University and Princeton University provide a nice selection of GIS Sites from around the world.

The Center for International Earth Science Information Network (CIESIN) at Columbia University, works at the intersection of the social, natural, and information sciences.

GIS for the Humanities from San Antonio College.