This site has science movies and a wide variety
of other interesting things for kids to explore.
http://www.brainpop.com/

This site is a friendly, non-technical place to come
and "play" with the laws of physics.
http://www.fearofphysics.com/index.html

NASA's site has many topics to explore.
http://kids.earth.nasa.gov/

Helping Your Child Learn Science has many
helpful pointers for parents.
http://www.ed.gov/pubs/parents/Science/index.html

This site has ideas to enhance learning.
http://school.discovery.com/

Many science sites are listed here..
http://www.kidskonnect.com/ScienceSites/ScienceSitesHome.html

Science NetLinks has lesson plans and other resources for teachers.
http://www.sciencenetlinks.com/matrix.cfm