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.
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.
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.
World Bank Statistical Capacity Building Project
The World Bank's Statistical Capacity Building Project "provides resources to help ... develop better statistical capacity that advances the national and international monitoring of development policies and goals." The project is in part an outgrowth of "outcomes-based" approaches to development that place greater emphasis on attemping to actually measure development and the impact of national and international policies intended to promote it. The resources here include various reports on the quality of gathering of data/statistics in individual countries, as well as a database of "statistical capacity indicator" scores.