For our future engineers: Science from Trash!
Science Fair Projects - Splitting Water into Hydrogen and Oxygen
make an electroscope - electrons - atoms - experiment~ATS
Easy Hydraulic Machines style and other engineering projects for kids
Perhaps a science fair project? Make a Photon Flower That Lights Up When You Water It with Lemon from Instructables
is a bit too much glueing, but several on the site are simpler. basic posicle arm and a car.Hydraulic projects for kids!
Lesson 8 : Energy : Science Fair: Solar Heating and Designing of a Solar Cooker
HOT Air Balloon Fun project to do with your kid for the science fair. Good way to show the effects of hot air.