Franklin Roosevelt was an avid stamp collector. You can find this fun online exhibit on his stamp collecting as well as the stamps he helped design as president from the Smithsonian's National Postal Museum. FDR's first stamp design was to help promote Admiral Byrd's second Antarctic expedition:
The President's sketch, calling for a commemorative-size stamp arranged vertically, shows the eastern coast of the United States and South America, the western areas of Europe and Africa, and the routes of Byrd's trans-Atlantic, North Pole and South Pole flights.
In preparing the model for this stamp, the artists at the Bureau of Engraving and Printing, where the stamp was produced, took certain liberties with the "chief’s" suggestions, but obviously retained FDR’s major concept. Instead of showing only certain coastal areas, a globe was implemented, to show the routes of Byrd's journeys more clearly. Later, when this original sketch was reclaimed from the Bureau of Engraving and Printing, the President autographed it "Franklin D. Roosevelt" in pencil and dated it. The Polar Stamp was issued on October 9, 1933.
President Roosevelt insisted that the Post Office Department carry mail bearing this stamp to the expedition base in "Little America" for canceling and return. The President understood that collectors would pay dearly for the special cancellation. Each collector paid 53 cents per cover to get the "Little America" postmark - 3 cents for the stamp, and 50-cents to finance Byrd's expedition. Admiral Byrd was, of course, deeply appreciative, and wrote the President: "Dear Franklin: I am greatly moved by the wonderful way in which you have helped me at this time of great crisis in my life. My expedition has been so costly that I have been threatened with bankruptcy. ... It is rather beautiful, Franklin, the way you have come to the rescue of your old friend." Roosevelt's sole request of Byrd was "a letter for my stamp collections." Naturally, FDR received quite a few.
FDR once sent a present of some stamps and an album to the son of an important Massachusetts family, who then wrote him back thanking him for the stamps. That boy just happened to be Bobby Kennedy. You can read FDR's birthday note to Bobby as well as Bobby's response from the FDR library (they are buried in this file...not sure why these are all mashed together like this, but oh well, still fun to see).