This teacher-created site invites kids of all ages to use science to create toys.  There are many video tutorials to guide you through a project using common household materials and no equipment more complicated than what you would find in your kitchen.  Build a robot voice box, snake charmer’s duck call, a robot hand or an air rocket, just to name a few. 

All Science Fair Projects has links to more than 500 projects in biology, chemistry, physics, microbiology, biochemistry, medicine & health, environmental science, mathematics & computer science, engineering, earth science, and behavioral science. Each project includes the difficulty and grade level. The database can be sorted by popularity and level of difficulty.

Science Quest Mobile Lab has youtube videos of several experiments kids can do with adult supervision.

From site:  Make a Science Fair Splash! You can turn the investigations that you see on DragonflyTV into your own science fair project! Every investigation featured on the show has its own Web page where the kids describe exactly what they did. It follows what they asked, what kinds of experiments they tried, and what they found out. Then, we added other ideas for even more projects for you to try.

Download the DragonflyTV Educator’s Guides to get kids started on their own inquiry investigations. The activities are developed with the National Science Teacher’s Association. They’re aligned with today’s science standards, and they’re ideal for the classroom or for after-school programs.

Janice VanCleave, teacher, scientist and award-winning author, explains the scientific method, and provides project ideas in astronomy, botany, chemistry, earth science, geography, physics and zoology.  She also has an “Ask Janice” segment where kids can ask all types of science questions.