The Number of Countries in the World

By Most Accounts, 193 is the Correct Answer

United Nations
There are 192 members of the United Nations. Unfortunately, the number 192 is too often used to represent the number of countries in the world. Although this number represents almost all of the countries in the world, there is still one country (the Vatican City) that is independent and has chosen not to become a member of the U.N. so 192 is not the number of countries in the world.

The One Outsider
Taiwan meets most, but not all of the requirements of independent country or state status. However, due to political reasons, it fails to be recognized by the United States and much of the rest of the world. If it were recognized, it would be considered a country.
Taiwan was actually a member of the United Nations (and even the Security Council) until 1971, when mainland China replaced Taiwan in the organization. Taiwan continues to press for full recognition by other countries, to become "part of the club" and fully recognized worldwide but China claims that Taiwan is simply a province of China.
source: About.com-Geography