I really like the bucket books for read aloud. A friend who teaches fifth grade used "How Full is Your Bucket?" last week with her class. After reading the book aloud, she had each child write a compliment to every other child in the classroom and place them in small buckets she had purchased at Target.
The books address bullying indirectly, but they are good for building positive relationships.
I just read "Mean Girls" because of a situation my own child was in. I learned a lot about how and why girls bully.
My fifth graders liked the Chrissa movie though it was a little more extreme bullying than is usually a problem in my class. I read Thank You Mr Fauker by Patrica Polacco, The Sneetches by Seuss. I read Mr. Peabody's Apples to talk about spreading rumors.
The Recess Queen and Jungle Bullies are really good picture books, and How To Eat Fried Worms is a good chapter book. Jungle Bullies is really for younger children, but someone might be reading this that is looking one for preK through first grade.