The U.S. government's open data portal. Limit by file type to locate textual data resources. Files are accessible as XML files, PDFs, HTML files, or TXT files.
Searches documents from all science-related agencies in the US government. A great place to look for governmental reports or research if you're not sure which agencies might be involved.
An open repository hosted at Harvard in which authors can deposit their replication datasets. Includes datasets from important journals and research projects, such as American Journal of Political Science and survey organizations like Gallup.
Like science.gov, but international in scope. Many links do not go to the full text, but can give you some leads on which agencies and organizations might collect data.
This is a great starting point! The Statistical Abstract is the U.S. Census Bureau's annual collection of national (and some international) statistics. The best part of the Statistical Abstract is that each table of data includes information on who collected the data and where to find more.
The U.S. government's open data portal. Limit by file type to locate textual data resources. Files are accessible as XML files, PDFs, HTML files, or TXT files.
Search summaries of statistical publications, then link to the full-text of selected publications on Statistical Universe and government Web sites. This comprehensive database includes the three major statistical indexes (American Statistics Index, Statistical Reference Index, and Index to International Statistics).