The World Factbook is published annually by the United States Central Intelligence Agency (CIA), and the web version is updated weekly.
The World Factbook provides information on the history, people, government, economy, geography, communications, transportation, military, and transnational issues for 267 world entities. The available information includes: political and physical maps of the major world regions, other maps, and the Flags of the World. This is a handy reference work for basic and reliable statistical data on the countries of the world. The appendices and the The World Factbook Users Guide can lead you to additional interesting data on the website.
Also potentially of interest to you: The CIA publishes and updates the online directory of Chiefs of State and Cabinet Members of Foreign Governments monthly. This directory is a reference aid and includes as many governments of the world as is considered practical, some of them not officially recognized by the United States.