USA Presidents This is an outstanding site which has information on the American Presidency. It also has individual biographies of each President. This is an easy to navigate and read site. It is fairly new and I expect it to rank well in the search engines in the future.
From the site:
About the Presidency
The President of the United States is the head of state of the United States . Under the U.S. Constitution , the President is also the chief executive of the federal government and commander in chief of the armed forces .
Requirements to hold office
Section one of Article II of the U.S. Constitution establishes the requirements one must meet in order to become President: The president must be a natural-born citizen of the United States, at least 35 years of age, and a resident of the United States for 14 years.
Under the Constitution, the President serves a four-year term. Amendment XXII (which took effect in 1951 and was first applied to Dwight D. Eisenhower in 1952 ) limits the President to two terms.