A while back someone suggested creating a map of Europe with all the fictional countries on, and I'm trying to create a list of them...
Europe
Belsornia -- From which Elisaveta of the Chalet School hies -- Somewhere between the Anschluss and the Soviet Union, near Mirania.
Guilder -- from The Princess Bride, next to Florin.
Florin -- from The Princess Bride, next to Guilder.
Mirania -- see Belsornia.
Latveria -- small Eastern European country ruled by Doctor Doom, of Marvel Comics fame.
Symkaria -- adjacent to Latveria, same source.
Americas
San Theodoros -- South American dictatorship to which Tintin the boy reporter travels (and at one point is inadvertently appointed a colonel in the army of).
Nuevo Rico -- hostile neighbour of San Theodoros, same source.
San Seriffe -- a small fictional island created by a (real) Guardian reporter for purposes of getting a delegates' pass at an international conference.