I put together an event for our local homeschool group. The general idea is that kids can try their hand at building stuff. I called it "Craft Engineering". The original idea was to build bridges or towers, but because the ages ranged from 3 up to 12, and because I didn't want to prescribe how to build the things, the kids built pretty much what they wanted. Oh, and it wasn't a competition, just a fun time.
The materials are floral foam cut into blocks and uncooked pasta of various types.
First event in November:
Second event in December: