One of the greatest movie-song combos of all time is "Al Otro Lado del Rio" (The Other Side of the River), in the movie, The Motorcycle Diaries. (Remember when we put this song on every mix CD for a while?)
The movie, if you haven't seen it, tells the story of a young Che Guevara, before his political life really took off, and a journey he takes with a friend. The song, if you haven't heard it, is both melancholy and hopeful. Simple and beautiful. The song and the film would be utterly different beings without each other.
I just learned that Che Guevara, the man, not the moviemyth, was actually completely tone deaf and "rhythm deaf."