This month my kids and I have been doing activities and crafts that center around Earth day for the month of April. The first of these (and my favorite) was using container lids left over and saved from different things, like milk jugs, to stamp the planets of the solar system. We took several different sized lids and set them out with paints and brushes and two pieces of paper tapped together. We painted the flat side of the lids and stamped the sun and planets in order (my six year old stuck to that plan, my three year old just stamped wherever).
We used a picture of the solar system for guidance and my son labeled the planets. We also read a book called, If You Decide To Go To The Moon by Faith McNulty, which shows a kid preparing for a trip to the moon in a rocket. He gets supplies and games and during the trip talks about being lonely. He gets out on the moon and walks around in his space suit. He discovers that the moon is lacking a lot of the lovely things that the Earth has. On his way home he realizes how special the Earth is because it is the only place with the ability to have life which creates so much beauty and so we really need to protect the Earth.
This was a super easy project that we put together last minute but is great for science, art, motor skills, and writing (if you label planets).