The Help Me Be Good series of books by Joy Berry is terrific.  These little books tackle countless behaviors (interrupting, being a bad sport, being forgetful, being rude, complaining, disobeying, lying, whining, and the list goes on and on).  Basically there is a book for every less than desirable behavior a child might exhibit.  The books are straight forward and provide a great beginning for further conversation about the topic whether in a class setting or within a family.  They are simple enough to be a resource which could be used for preschool aged children, but they could be easily used with older children as well.