George Washington
James Monroe
Andrew Jackson
James Polk
James Buchanan
Andrew Johnson
James Garfield
William McKinley
Theodore Roosevelt
William Howard Taft
Warren G. Harding
Franklin D. Roosevelt
Harry S. Truman
(Lyndon B. Johnson)
Gerald R. Ford

Notes (in chronological order):

William McKinley's Masonic membership has not been confirmed 100%, though his name does appear on several lists. Hopefully, someone will be able to provide a definitive yes or no.

William Howard Taft was made a Mason At Sight by the Grand Master of Ohio and later raised to Grand Master of Ohio in 1909.

Harry S. Truman was also Grand Master of his home state, Missouri.

Lyndon Johnson was an Entered Apprentice, but never progressed beyond that degree.

Ronald Reagan is not a craft Mason. He was made an honorary 33rd degree Mason by the Southern Jurisdiction of the AASR and an honorary member of the Imperial Council of the Shrine, but he was never entered, passed, and raised as a Mason, nor was he ever made a Mason at sight. (Source: Robinson's Born in Blood)

Bill Clinton is not a Mason, though he was involved in DeMolay for a time.

Many other leaders in government have been Masons: "They have included fourteen Presidents and eighteen Vice Presidents of the United States; a majority of the Justices of the United States Supreme Court, of the Governors of States, of the members of the Senate, and a large percentage of the Congressmen. Five Chief Justices of the United States were Masons and two were Grand Masters. The five were Oliver Ellsworth, John Marshall (also Grand Master of Masons in Virginia), William Howard Taft, Frederick M. Vinson and Earl Warren (also Grand Master of Masons in California.)" -- Henry C. Clausen