ICPSR (Inter-University Consortium for Political and Social Research)
http://www.icpsr.umich.edu/
The ICPSR is one of the largest collections of quantitative data in the world. The archives contents cover a very wide range of topics, with household surveys, health conditions and health care, and public opinion being particularly strong points in the collection. Emory's local ICPSR representatives are Ms. Jennifer Doty and Dr. Robert O'Reilly. The ICPSR is also available via Databases at Emory. If you need to access the ICPSR and its data from off of campus, please see this notice and these instructions from the ICPSR.
Council of European Social Science Data Archives (CESSDA)
https://www.cessda.eu/
CESSDA is a consortium of national data archives from various European countries. CESSDA's data catalogue offers a central point of access to the holdings of the individual archives. Please note that different archives will have different access policies and different practices for documentation and dissemination of data files to researchers from non-European countries. The UK Data Archive, GESIS (Leibniz-Institute for the Social Sciences), and the Centro de Investigaciones Sociologicas are all generally willing to allow non-European researchers access to datasets upon registration.
Harvard Dataverse Network (DVN)
https://dataverse.harvard.edu/
Harvard's Dataverse Network is an eclectic collection of datasets and data collections, including replication datasets for articles on topics such as political competitiveness in post-war Latin America or the effect of IMF programs on government spending, ongoing research projects on topics such as manifestos of regional political parties and ideology scores of state legislators and perceptions of electoral integrity, organizations such as development NGOs, groups such as networks of economists at different universities, and replication archives for academic journals.
National Bureau of Economic Research (NBER)
https://www.nber.org/research/data
In addition to its work on business cycles, the NBER has an eclectic data archive that covers topics such as cross-national technology adoption, manufacturing productivity, financial openness and exchange rate regimes, and economic policy uncertainty. Its data archive also covers topics such as labor markets, health economics, and population demographics.
Roper Center for Public Opinion Research
https://ropercenter.cornell.edu/
The Roper Center is one of the country's premier centers for polling data, with holdings dating back to 1935. While the bulk of the Center's data are for national polls, it also includes many state-level polls as well. The iPOLL interface may be of particular use because it allows users to search through surveys at the question level. Roper also has a large compilation of Presidential approval ratings. See https://ropercenter.cornell.edu/data-highlights/featured-projects for other Roper projects related to public-opinion data and see https://ropercenter.cornell.edu/data-highlights/featured-collections for some of the highlights in Roper's data collections. The Roper Center is also available via Databases at Emory.
World Bank Data Catalog
https://datacatalog.worldbank.org/home
As part of its Open Data Initative, the World Bank has opened up access to dozens of its data collections and compiled into a single data catalog. The holdings here range from larger databases covering multiple topics to more narrowly-focused collections associated with particular research projects. You can also search for World Bank data by country or by looking for specific indicators.
Qualitative Data Repository (QDR)
https://qdr.syr.edu/
Syracuse University's Qualitative Data Repository "curates, stores, preserves, publishes, and enables the download of digital data generated through qualitative and multi-method research in the social sciences." Scholars can access collections of qualitative data from research projects. The QDR also provides extensive extensive guidance and resources for managing qualitative data.