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.
Marble Races with a cheap pool noodle (occupies the kids for hours.) Did this, but instead of cutting the pool noodle, the marble is small enough to fit inside the full noodle to roll down. Then can use the noodle for other things too!