Here are some links to help you with science experiments:
Building Volcano Models 
Build a variety of volcanos from very easy to more complex.
Explore Science 
A great site to test scientific principles. (Shockwave plug-in required to view this web site.)
Bill Nye the Science Guy 
Web site for the TV show (Flash plug-in required to view this web site.)
Whelmers - McREL's Accessible Science Series 
Experiments for all ages.
The Why Files 
Popular science experiments that change every two weeks.
You Can! 
Beakman's World web page.