Fun with water, great recycled plastic bottle project. This could be pretty if you used wine bottles. It's just a matter of figuring out how to cut a hole in the side.
Rainbow Science for Kids: Homemade Spectroscope - Buggy and Buddy
Turn milk into plastic with vinegar! Such a cool science experiment for kids, preschoolers and adults too
Walking Water Science Experiment for Kids - Coffee Cups and Crayons