It was the last song Rodgers and Hammerstein composed together. It appears twice in the film; near the end when the Von Trapp family sings it at the festival as a patriotic hymn, rousing the audience to join them. Good as that scene is, I prefer the first time it appears - when the children learn that their father knows how to play the guitar. He simply strums a few chords and tenderly sings to the children.
So - how about a few other versions of the song? Here is one by a popular Iranian singer who performs it as a protest against the current regime, just as Georg sang it to protest the Nazis:
And here is a link to a young girl who sang it on Britain's Got Talent and broke down in the middle: http://www.youtube.com/watch?v=R2SxoBTkfNQ
She did get a second chance - thanks to none other than Simon Cowell himself...