Ok todays post is another make it post. While I've not made this yet myself it is for an outdoor science day I'm doing soon.
Make your own.... catapult! These look really cool and could be great if we ever get any hot weather to fire water bombs. You can just use garden canes, elastic bands and plastic cups.
I've got a couple of links to point you at, but I'm sure kids could come up with their own designs to. Anyway the sites are here and here.
Be sure to head over to Jo to see the other posts.