Definitely follow the link @N F C has left for you for treats ideas. Any salad greens and cabbage are great for chickens, keeps the liver healthy and there are many trace minerals and antioxidants for good health.
Welcome to BackYard Chickens from Maine! Mealworms are great treats for chickens (any and all treats should be used in moderation). Broadleaf Plantain has been a favorite for my chickens.