THE CURIOUS GARDEN by Peter Brown is one of my absolute favorites for its simplicity, eco-optimism, and subtle humor.
INTERSTELLAR CINDERELLA by Deborah Underwood is another stellar (ha!) book for its humorous and empowering twist on a classic.
MY BLUE IS HAPPY by Jessica Young is a fantastic way to introduce kids to different perspectives and associations, and to show that it's okay to view the world differently.
MARISOL MCDONALD DOESN'T MATCH by Monica Brown is a colorful, bilingual (English/Spanish), delightful book about individuality and confidence.
And finally, anything and everything by Peter Reynolds, especially THE NORTH STAR and SKY COLOR (really, the whole Creatrilogy).