There is always a lot of chatter about summer reading lists and I love picking up tips from other folks. I just have to put in a major plug for Mo Willems. If you have an early reader Mo's books contain all the joy and whimsy of Seuss without the fatigue of so many pages.
Mo (I'm pretty sure he'd want me to call him Mo and not Mr. Willems) has written a number of children's books following his Emmy-award winning stint at Sesame Street. "Don't Let the Pigeon..." books are delightful and allow your toddler to shout out "NO!" with abandon. The "Knufflebunny" stories tell the tale of a girl and her lovey with delightful illustrations.
But my heart belongs to Gerald and Piggie. They are best friends despite and because of the fact that Gerald is a pragmatist and Piggie cannot surpress her joie de vivre. My early reader delights in their escapades and triumphs as he reads "the whole book."