D. William Spenser's The Faerie Queene follows the quests of several knights who seek to better themselves, but symbolically gives honor to Queen Elizabeth and her kingdom.
An allegory is a story that has two meanings. The first is the basic, in your face, meaning of the story. In this example, the basic story is the knights on their quests. The second level of meaning is the symbolic meaning. The story represents some bigger subject outside of the story. In this example it symbolically shows honor to the Queen and her kingdom.
Another allegory is The Lorax. The first level of meaning is to save the trees. The second symbolic level is corporate greed shown mostly through the actions of the Onceler.