ICPSR maintains a data archive of more than 500,000 files of research in the social sciences. It hosts 16 specialized collections of data in education, aging, criminal justice, substance abuse, terrorism, and other fields.

The National Archive of Criminal Justice Data (NACJD) provides datasets that can help guide the exploration and extension of research ideas for topics connecting technology and criminology.

Provided by the Roper Center for Public Opinion Research at Cornell University, Roper iPoll is the largest collection of public opinion poll data with results from 1935 to the present. Roper iPoll contains nearly 800,000 questions and over 23,000 datasets from both U.S. and international polling firms. Surveys cover any number of topics including, social issues, politics, pop culture, international affairs, science, the environment, and much more. When available, results charts, demographic crosstabs and full datasets are provided for immediate download.

OpinionArchives provides electronic archives for journals of opinion, including The Nation, Commentary, The New Republic, Commonweal, Dissent, NACLA, Orion, American spectator, National review, Harper's magazine, New York review, and the New Yorker. The OpinionArchives metasearch tool provides cross-journal searching for all titles in the archive.

Users that have an email address with the extension @uiowa.edu can self-register by visiting: https://ropercenter.cornell.edu/ipoll/login although registration is no longer necessary to search or download when connected to the campus network.
Once users enter their email address, they should receive an activation email with a link to complete registration

IPoll is a comprehensive, up-to-date source for US nationwide public opinion. A full-text retrieval system, the iPoll online database is organized at the question level, providing the tools to sift through nearly a half million questions asked on national public opinion surveys, 1935 to present. Surveys archived in the Roper Catalog were originally gathered by academic, commercial and media survey organizations such as Gallup Organization, Harris Interactive, Pew Research Associates, and many more.

Users have a choice to either create an account to log-in using their e-mail address or click a button to log-in as a guest
SimplyMap is a web-based mapping application that lets users quickly create professional-quality thematic maps and reports using demographic, business, and marketing data for the United States. NB: 5 concurrent user limit.

Social Explorer is an online research tool designed to provide quick and easy access to historical census data and demographic information. It creates fast, intuitive, and appealing maps and reports to help users visually analyze and understand demography and social change throughout history. The site currently includes the entire US Census history from 1790 to 2000, all annual updates from the American Community Survey, and the Religious Congregations and Membership Study from 1980 to 2000.
Users may wish to create an individual account to save maps and other features in Social Explorer.

The U.S. Bureau of Labor Statistics (BLS) provides data in the broad field of labor economics and statistics.

Discover data on free statistics of irreproducible research. The purpose of this project is to facilitate the creation, maintenance, and permanent storage of statistical computation objects that empower authors to publish reproducible and reusable research (in the form of a Compendium) through a series of web services. FreeStatistics.org is closely linked to Wessa.net: a project that provides Web-Enabled Scientific Services & Applications with the purpose to make statistical science easily available to anyone.

Historical Statistics of the United States represents data series from earliest times to the present and has long been a standard source for quantitative indicators of American history. Broad topic categories include Population, Work and Welfare, Economic Structure, Economic Sectors, and Governance and International Affairs.

The ProQuest Statistical Abstract of the United States is the authoritative and comprehensive summary of statistics on the social, political, and economic conditions of the United States. The online version includes monthly updates to tables, deep searching at the line-item level, powerful facets for narrowing search results, image and spreadsheet versions of all current and historical tables, along with links to provider sites.

Provides access to statistics and studies gathered by market researchers, trade organizations, scientific publications, and government sources on over 600 industries.