What I really enjoyed about book III was not the individual characters as allegories, but rather the whole book as one giant allegory. Many of my fellow classmates have discussed how each character represents a certain kind of chastity, or for other characters a certain kind of sin such as gluttony. However, I think this interpretation is a tad bit too focused.
The four characters that represent chastity as a whole are Britomart, Amoret, Florimell, and Belphoebe. Every encounter they have with men (or sometimes women) trying to take their virginity is representative of a trial one must face to remain chaste. The first, and most obvious, is the physical trial. These encounters occur when our faire maidens are confronted with men who simply lust after them.
Florimell has a great many of these encounters, but one that comes to mind is the fisherman. He tries to seduce her but she resists. Eventually, he tries to rape her but she is saved by Proteus, the shepard of the seas. Proteus also tries to seduce her by shapeshifting into various things. These shapes all represent different physical manifestations, but also carry other significance. When he shapeshifts into a king, the temptation to break her chastity is the power that comes from being a king. When he shapeshifts into a knight, the temptation is protection and an honorable husband. However, when these attempts fail Proteus becomes angry and throws her into a dungeon. Malecasta also tries to tempt Britomart, even though Britomart is oblivious to her motives. Malecasta hosts a lavish feast, displaying her wealth and power to tempt Britomart into being with her. Britomart is of course not tempted since she knows Malecasta is a woman, but it was a trial of temptation nonetheless.
Book III’s central theme is chastity and the trials that one must face in order to remain chaste. There are two broad categories of characters in the book: the characters that represent chastity and the characters who try to tempt the chaste characters. As is often the case with allegories, there is no one to one ratio, theme to character. Instead Spenser defines two broad groups of characters to represent his main theme and the trials chaste persons must face.