I started collecting magnets last year during our vacation to Atlanta, Georgia. The first of my DC trip is the one from the Smithsonian's National Zoo. I had to get one with the red panda on it.
It also flips and you can see an elephant if you prefer.
I got this one at the National Museum of American History, but this one was actually more a generic one of the Smithsonian Museums in general.
Now I did get one of the Smithsonian's Natural History Museum.
I really liked this one from the National Air and Space Museum. It's a space shuttle "flying" in space though with the help of H20.
Of course I had to get one of the White House.
Unlike the unofficial one from the White House, I got this one at U.S. Congress.
Found this one at the Jefferson's Memorial tiny gift area. It's got the notable memorials and monuments from The National Mall on it.
I got this one at the Supreme Court of the United States.
And the National Gallery of Art, which is ironically, not very artistic when they came to make the magnet.
So here's my whole collection so far from all parts of the United States I've seen so far.