Pop Rocks Summer Science Experiment for Kids - This has got to be one of the coolest experiments. Simple to do, but will amaze kids from Preschool and Kindergarten to 1st-6th grade.
This site is FULL of materials you can make into engineering projects by recycling materials! Fantastic! Science, technology, and engineering for any age!
Fun Kids Crafts, Science Projects, and More | Land Projects | LooLeDo | Crafts for Kids
Make a catapult from a milk carton cap, pencils, rubber bands and an old tissue box.