More recent presidents:
Obama: Gryffindor. The charisma, the courage, the grace--yeah. Whatever else anyone says about him, he's a Gryffindor.

Bush GW: much as I'd like to put him in Slitherin, he's just not smart enough. I'd have to put him in Hufflepuff.

Clinton: Ravenclaw. The man might not be able to keep it in his pants, but he's brilliant.

Bush GH: Slytherin, without a doubt. Man's as slick as a greased weasle.

Regan: Slytherin, but surprisingly, he'd be more along the lines of Horace Slughorn than the really greasy baddies.

Carter: Egads! Hufflepuff all the way!

Ford: I call Hufflepuff as a default, though he could go into Gryffindor as a default too.

Nixon: you called it! Slytherin.

Johnson: Ravenclaw. He was a downhome boy, but brilliant. He also knew when to call it quits!

Kennedy: Gryffindor (though you could make a good case for Slytherin too.)