Harvard Dataverse Network (DVN)
Harvard's Dataverse Network is an eclectic collection of datasets and data collections, ranging from replication datasets from articles to institutional data collections. Many development NGO's and research organizations use Dataverse, including the Jameel Poverty Action Lab, Population Services International, the International Food Policy Research Institute, and the Center for Global Development. Dataverse also hosts more esoteric, specialized data collections, such as this collection of data on financial inclusion and access in Kenya.
UNData, which is available from the United Nations Statistical Division, is a portal for extracts of data compiled by various United Nations agencies and by other international organizations such as the World Tourism Organization and the International Telecommunications Union. UNData is a replacement for the old UN Common Database.
United Nations Human Development Reports (HDR)
The HDR is an annual report from the United Nations that scores and rank countries on various indicators of "development" broadly defined. The current incarnation of the HDR provides access to both past and present reports and a variety of tools for visualization and downloading of HDR data and statistics. For additional visualization of development-related indicators, see Gapminder. Data from some earlier reports are available via Carleton University's Country Indicators for Foreign Policy site.
World Development Indicators (World Bank)
The World Development Indicators provide convenient access to hundreds indicators on over 200 countries and territories. Data are available annually from 1960 forward, with variation across countries and indicators. The database is part of the Bank's Data Catalog of statistical databases and other data collections. The WDI is also accessible via Databases at Emory and on CD-ROM in the Data Center. There are also multiples tools available for importing WDI data directly into programs such as R and Stata.
World Bank Data Catalog
As part of its Open Data Initative, the World Bank has opened up access to dozens of its data collections and compiled into a single data catalog. The holdings here range from larger databases covering multiple topics to more narrowly-focused collections associated with particular research projects. You can also search for World Bank data by country or by looking for specific indicators.