You could get some star stickers or magnets or felt/velcro pieces and play what DS4 calls the constellation game--we take turns making "constellations" with the pieces and guessing what the other person has created (it's kind of like finding pictures in the clouds).
We also make a lot of playdoh planets, sing a bunch of space songs (I have a whole iTunes playlist set up), and read space books. DS is also just happy drawing picture after picture of the solar system. There's also a fun kids TV show called the Zula Patrol that teaches about space and planets--one of their dvds is more planet and space focused than the other.
If you're thinking of going low tech for a globe, I'd recommend getting one that's inflatable and see-through. Makes it easier to see what's on the other side from where you are.
