Great resource for parts and kits
Some ideas here for 3rd graders who have studied sound
A fun project from Spark Bang Buzz, good for 4th grade. Explore the site for more inspiration
Well organized list of ideas by subject (electricity, math, life sciences, etc.)
One explanation of the laser pointer sound experiment
Explore this weblog deeply for all sorts of year-round ideas, science fair included.
Power a super-bright LED from a low-voltage battery with a few bits of wire and a toroid core