Toothpick and Gumdrop Construction: Cost: 1 dollar for the box of toothpicks and 1 dollar for each boy a giant box of gumdrops SOO FUN! Definitely will do this again. Great for Cub Scouts - could use for constellations or for science molecules.
Could also connect a bunch of locks and put all the keys on a key ring. Lots of pictures of latch, lock, etc ideas for montessori type preschool. This lock one could be made with 2 boards, some o-rings, and some locks from Dollar Store.