Who is the oldest former president still alive now?

As of February, 2012. there are four US ex-Presidents still alive. These are, in order of Presidency:

Jimmy Carter (born October 1, 1924 ) , lives in Atlanta. GA

George H. W. Bush (born June 12, 1924), lives in Houston, TX

Bill Clinton (born August 19, 1946 ) , lives in New York City

George W. Bush (born July 6, 1946 ), lives near Crawford, Texas.

The most recent presidents to die were Ford in December 2006, Reagan in June 2004/