http://www.abc.net.au/science/surfingscientist/
An arrangement of demos, lesson plans and videos spanning multiple science fields geared mostly to elementary students.
http://galileo.phys.virginia.edu/outreach/8thGradeSOL/home2.htm
Activities correlating to Virginia 8th Grade Physical Science SOLs
http://www.stevespanglerscience.com/experiments
A plethora of science experiments over a range of topics. The site also has science kits, supplies and gadgets for sale.
http://portal.acs.org/portal/PublicWebSite/volunteer/chemambassadors/futurechemists/CNBP_023888
ACS has come up with a guide to becoming a resource in the classroom, including planning classroom visits, how to discuss topics with children, and sample activities and demonstrations to do with students.
http://www.elmhurst.edu/~chm/demos/index.html
This site has a list of chemistry demonstrations, organized by household materials, and lab chemicals. Each one has directions and an explanation. Doesn’t appear to be updated since 2003.