The Jolly Postman by Janet and Allan Alhberg

I loved using this book for letter writing (a lost art with the texting and email world now upon us!).  Check out these ideas - http://www.readwritethink.org/classroom-resources/lesson-plans/genre-study-letters-with-322.html , http://teachers.net/lessons/posts/730.html

There is also a holiday version of the story.  Fifteen years ago, long before anyone else thought of tucking actual letters and notes inside a book, Little, Brown published The Jolly Postman by Allan and Janet Ahlberg. This wonderful book gave children a chance to read letters sent from one fairy tale or Mother Goose character to another. Among the funny notes was one from Jack, who lolled on a sun-drenched island, thanking the Giant for the gold that let him afford such a nifty vacation. All this amusing correspondence was deftly illustrated and the book attracted hordes of eager readers.