Enemy Pie by Derek Munson - how to turn a best enemy into a best friend is the basis for this effective message about how to handle relationships and conflict.
You Will Be My Friend by Peter Brown - making friends is harder than it looks and this is a great little story about friendship. The word "Will" in the title should definitely be emphasized when you say the title.
The Fruit Salad Friend: A Recipe for a True Friend by Maria Dismondy - the little girl in the book has all the ingredients to be a great friend (kindness, empathy, compassion, and more), yet she wonders what do you do when "friends" don't treat you with kindness? She finally discovers the recipe for lasting friendship.
Spaghetti in a Hot Dog Bun by Maria Dismondy - this book helps children deal with hurt, consider options, and remember to be kind and do the right thing, regardless of how others are treating you.
The Jelly Donut Difference: Sharing Kindness with the World by Maria Dismondy - a brother and sister don't always get along and can even be downright mean to each other. Does the power of kindness, generosity, and caring show them how to get along in life? An act of kindness can be life changing!
Those Shoes by Maribeth Boelts - Jeremy wants the popular shoes but his grandmother tells him they don't have room for "want", only "need", and what Jeremy needs are new boots for winter. This is a warm and very real story that helps Jeremy realize that the things he has are worth more than the things he wants, because along the way this lesson helps him make a new friend.
Strictly No Elephants by Lisa Mantchev - this story captures both the magic of friendship and the joy of having a pet. The story deals with being excluded and how that can be overcome.
Edwurd Fudwupper Fibbed Big by Berkeley Breathed - the cover of this book makes you want to read it from start to finish. Edwurd constantly tells fibs, but one day he tells such a whopping lie that the army, air force, and the dogcatcher are called to reverse the damage. Super cute illustrations!
One Smile by Cindy McKinley - how one small act of kindness can affect so many people. It's hard to finish this book without getting a lump in your throat. This is a heart-warming story that shows it only takes one smile.
Nerdy Birdy Tweets by Aaron Reynolds - a subtle message about social media pitfalls and the importance of nurturing our real-life friendships told through a humor-filled story to which kids can relate.