Here are some links to help you with science experiments:
Building Volcano Models
Build a variety of volcanos from very easy to more complex.
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.
Beakman's World web page.