This site houses a large Data Catalog, and there are links to other data archive sites.
"The Odum Institute maintains one of the oldest and largest catalog of machine-readable data in the U.S. It has an extensive collection of U.S. Census data, including one of the most complete holdings for 1970 Census files. Other major sources of data include the North Carolina State Data Center, which distributes North Carolina census data; and the National Center for Health Statistics."
Students may find this site as or more useful than ICPSR.