Several datasets on cases heard before the Supreme Court of the United States, 1946-present (with a lag of 1-2 years). Datasets are available in Excel, Stata, SPSS, and SAS formats.
Several datasets on armed conflict, 1946-present. Some datasets are georeferenced.
Websites for the Secretaries of State for All Fifty States
Links to the Secretary of State websites for all states in the U.S., plus Puerto Rico, Guam, and the U.S. Virgin Islands. Typically, election data for each state can be found on the website for its Secretary of State office. From the National Association of Secretaries of State.
Dozens of governance indicators gathered from sources including the World Bank and Freedom House. Features easily visualization and comparisons. By the Inter-American Development Bank.
Federal Election Commission Campaign Finance Data
Detailed, individual-level data on which people donated money to which candidates.
((DEAD LINK--TO BE UPDATED)) New York Times/CBS News Poll Archive
Searchable archive of New York Times/CBS News Polls since 1976. Raw data from these polls is available through ICPSR.
Download bulk data on campaign finance, lobbying expenditures, 527 groups, and the personal finances of politicians. A project of the Center for Responsive Politics.
Paul Hensel's International Relations Data Site
Maintained by a professor of political science, who says, "These pages are meant to include the most useful data sources on processes of international conflict and cooperation, as well as data covering international economic, environmental, political, and social data and data on similar topics for the United States."
((DEAD LINK--TO BE UPDATED)) Policy Agendas Project
1940s-present. Coded datasets of policy changes based on Congressional hearings, Congressional roll call votes, executive orders, State of the Union addresses, and more.
SIPRI: Stockholm International Peace Research Institute
Data on the weapons industry, arms transfers (1950-present), multilateral peacekeeping operations (2000-present), and military spending (1988-present).