Registry of Research data Repositories. "Over 1,000 listed research data repositories from all over the world making it the largest and most comprehensive online catalog of research data repositories on the web." Merged with databib.org
Large repository of harmonized datasets from a variety of sources, with global and time series coverage. Datasets allow complete access to datasets using customizable tables, graphs and maps, with numerous output formats available (Excel, PDF, delimited text, SAS, SPSS, XML, Shapefile GIS).
ICPSR (Inter-University Consortium for Political and Social Research) maintains an archive of more than 500,000 data files in the social sciences. Includes a bibliography of literature related to the data.