That's the Presidential Seal, as redesigned by Harry Truman to correct some weaknesses he felt existed in the original created by Rutherford B. Hayes for White House invitations.
If you like it there are plenty of companies
willing to sell you just about anything with the seal on it.
Important things require the use of the Great Seal of the United States, which is pictured on the back of the one dollar bill.Steve Bates
reports that the White House is upset by the use of the seal by The Onion
and has told them to stop.
Frankly I think Harry would approve of The Onion
, and I know he would agree with most of what I write. Hell, George H.W. Bush would probably approve of much of it.