The Ketchup Experiment! Kid friendly site with lots of neat experiments! It has one that makes a rocket out of a film canister, which would be good for an grade space unit, but it has to many kid friendly expiriments. Great site for any science teacher.
Balloon formed papier mache bowls covered in fabric! Can also be done over a bowl to give it the flat bottom necessary for placement on a table. Just put a thin coating of petroleum jelly on the bowl for ease of release when papier mache is dry.