General data by country

Banque Mondiale
Activities and development strategies of the World Bank, as well as thousands of articles and demographic, statistical, economic and social reports for each country of the world.
http://www.worldbank.org

World Factbook
American governmental service providing detailed information for nearly 200 countries in the world: map and geography of the country; demographic, political, legal, economic and commercial data.
http://www.odci.gov/cia/publications/factbook/index.html

The Economist
Economic, political and financial current events in the world, many sections reserved to the members but access to the countries section which offers detailed information for several dozens of countries in the world.
http://www.economist.com