Some hilarious examples that I have recently read, come from Bush Jr. There is a whole list of them on Slate, complete with a Bushism of the day! Of course, not all Bushisms are Malapropisms, some are, well....

A recent addition and an absolutely priceless one too:
"I know something about being a government. And you've got a good one."—Stumping for Gov. Mike Huckabee, Bentonville, Ark., Nov. 4, 2002