African Union. Has information on the Union and provides flags and basic data on all member states.
Eurostat. From the Statistical Office of the European Commission. Many publications, data sets, and tables available for free.
International Statistics. Links to all statistics programmes of the United Nations, of the United Nations Specialized Agencies (FAO, ILO, IMF, etc), and selected Autonomous Organizations (Eurostat, World Trade Organization, OECD, etc).
LABORSTA. Data on employment, unemployment, wages, labour cost, Consumer Price Indices, occupational injuries, strikes and lockouts, hours of work, etc. Covers over 200 countries or territories, some data going back several decades. From the Bureau of Statistics - International Labour Organization (ILO).
NationMaster. Country statistics from a variety of sources. Users can create graphs comparing countries on particular statistics.
ODS Search. Covers all types of official documents of the United Nations, starting in 1993, with older UN documents added daily. Also provides access to resolutions of the General Assembly, Security Council, Economic and Social Council and the Trusteeship Council, starting with 1946. Does not include press releases, UN sales publications, or the UN Treaty Series.
OECD Statistics Portal. Provides data by topic, e.g. health, education/training, information, communication, energy, environment, finance, technology, social welfare, etc. From the Organization for Economic Cooperation and Development (OECD).
OFFSTATS. Links to official statistics. Searchable by country, region, topic.
Organization of American States (OAS). Describes organization, charter, structure, mission, member states. Includes publications, documents, webcasts.
Population Reference Bureau. Provides data on 137 population, health, and environment variables for more than 220 countries, 28 world regions and sub-regions, and the world as a whole. (Not all countries have data on all variables.)
WHOSIS. The WHO Statistical Information System (World Health Organization)is a guide to health and health-related epidemiological and statistical information available from the World Health Organization.
World Bank Country Data. The data available from the World Bank are the most widely-used, official-source development data from the World Bank and other international agencies.