This is the new platform for accessing recent Census Bureau data. FYI, the Census Bureau stopped releasing new data in American FactFinder (AFF) at the end of June 2019 and transitioned to data.census.gov for data releases formerly on AFF. AFF will remain as an archive system for data and functionality that are not yet available in data.census.gov until early 2020.
General Social Survey (GSS) contains a standard 'core' of demographic, behavioral, and attitudinal questions, plus topics of special interest. Many of the core questions have remained unchanged since 1972 to facilitate time-trend studies as well as replication of earlier findings.
Panel Study of Income Dynamics (PSID) is the longest running longitudinal household survey in the world, starting in 1968 with a nationally representative sample of over 18,000 individuals living in 5,000 families in the United States. Information on these individuals and their descendants has been collected continuously, including data covering employment, income, wealth, expenditures, health, marriage, childbearing, child development, philanthropy, education, and numerous other topics.
The Statistical Abstract of the United States is an authoritative and comprehensive summary of statistics on the social, political, and economic conditions of the United States. Once provided free from the U.S. Census Bureau, now provided by ProQuest.
Pew Research Center regularly makes available the full datasets that underlie most of they reports. They typically do not publish the dataset at the same time as the report. That’s because it takes some time to complete all reporting for a given study and to clean and prepare the data for public release. The lag time varies by study, and some data (including surveys of certain populations, such as scientists or foreign policy experts) are never released, in order to protect respondent confidentiality. Survey data are cleaned to remove any information that could be used to identify individual respondents. Individuals will need to fill out a brief registration before downloading data.
Housed at the Institute for Quantitative Social Science (IQSS) at Harvard. Claims to host the world's largest collection of social science research. It holds data from many researchers and institutions in addition to Harvard.
ICPSR is one of the largest repositories for social science data in the world. Among the many topics covered, you will find statistics on crime, education, demographics, elections, religion, and much more.