Some general purpose, multiple topic collections and portals of statistical and data resources, often a good place to start research. Some are country/region-specific, such as those maintained by national statistical agencies.
Data archive of more than 250,000 files of research in the social and behavioral sciences. It hosts 21 specialized collections of data in education, aging, criminal justice, substance abuse, terrorism, and other fields
"The IHSN is a partnership of international organizations seeking to improve the availability, quality and use of survey data in developing countries. This informal network was established as a recommendation of the Marrakech Action Plan for Statistics."
"The Population Reference Bureau informs people around the world about population, health, and the environment..." - see http://www.prb.org/Datafinder/Topic/FullList.aspx for list of variables and http://www.prb.org/Datafinder/DatafinderSources.aspx for l