Marble slides. This site has lots of cool science activities using everyday materials.
Bill Nye Science Demos - quick and fun
Science - Rocks - FREE K-12 Lesson Plans & Games
Phases of the Moon
An explanation of why notebooking is such an effective tool for learning (Jimmie Lanley, The Notebooking Fairy)
Hands on science experiments to try
Tornado in a jar. Food coloring, glue, and water
JUST FOR FUN EXPERIMENTS: This website is dedicated to science experiments using candy. (pictures and EASY step by step instructions included)