Great fun with Puzzling Plates http://itunes.apple.com/us/app/puzzling-plates/id486435632?mt=8. The app allows you to move the plates around and it might be good reinforcement after a whole group hands-on activity.
You could read the Bluebonnet book “Far From Home”. It is set on another planet. Create a foldable comparing the Earth, Moon and a planet of their choice.
If you are like me and find that this book might be a bit boring for adult tastes, go ahead and use it as one of your balanced literacy books for one of your groups since I am sure the students will love it!