National Historical GIS (NHGIS) has data from all censuses and the American Community Survey together with other data like state census, and educational statistics. via the University of Minnesota
Integrated Public Use Microdata Series is the parent project of NHGIS and has extensive datasets on a wide variety of topics including health, education and international datasets.
Explore Census Data (U. S. Census Bureau) The census Bureau's main data portal.
QGIS Documentation This resource contains links to tutorials, technical support and more for QGIS.
