Data-Planet Statistical Datasets
Specialized Google search tool just for datasets.
Inter-university Consortium for Political and Social Research (ICPSR)
"An international consortium of more than 750 academic institutions and research organizations, Inter-university Consortium for Political and Social Research (ICPSR) provides leadership and training in data access, curation, and methods of analysis for the social science research community. ICPSR maintains a data archive of more than 250,000 files of research in the social and behavioral sciences. It hosts 21 specialized collections of data in education, aging, criminal justice, substance abuse, terrorism, and other fields." -- from the website hosted at the University of Michigan
"Statista gathers data from over 18,000 sources, including market reports, trade publications, scientific journals, and government databases."--from the library introduction page. (Rutgers-restricted Access)