44th President of the United States
Barack Obama is my 12th Cousin on my father's side (via the Beasley family) and is my wife's 8th cousin on her father's side (via the Roberts family). My common ancestor is Robert Brasseur born in France, died about 1665 in Maryland. My wife's connection is a few generations closer, through Jacob Duvall, born 1715, died 1796 in Maryland.
Likelihood of relationship: 50% for me, 70% for my wife.
If you would like to learn more about our president's heritage, click here. That site contains a really great presentation on the genealogy of President Obama. My wife and I both connect to him through the Brasseur/Duvall line in his tree, which is shown on the far middle-left. The tree contains many interesting stories about his relatives and even contains a bit of genealogy for his Kenyan heritage. It also explains how President Obama is related to George W. Bush, Dick Cheney, and Harry Truman, among others.