Leo Rosten's collection of stories about an American language class for immigrants, which I first heard through Kerry Shale's BBC Radio readings. These are both very funny and very well-written; in addition to his mastery of variably-mangled English, Rosten does a great job of capturing the pleasures and frustrations of teaching — something I wouldn't have recognised when I last read this ten-odd years ago! Highly recommended.
ISBN 0060136766.