Lots of ideas from the K-12 list, some of them followons to the Lawrence Berkeley Hall of Science Night...many very appropriate for K-5.
A fun explanation of an easy thing to do at home
Much more fun and easier than it sounds; never fails to impress
Scroll to very end
Ads in the paper copy, available at Borders Books, are good sources for parts and ideas. Adventurous 5th graders might find something of interest in the articles, too.
A fun project from Spark Bang Buzz, good for 4th grade. Explore the site for more inspiration
