This is a list of my favorite FREE science websites for homeschooling.
TryScience.org is a well designed, fun site with lots of activities (both online and for home) on a variety of science topics. I think the experiments are geared for elementary and middle school ages.
Chem4Kids is a great chemistry information site.
Computer Science Unplugged is a curriculum to teach computers without a computer.
Math / Science Nucleus offers a free traditional science curriculum that is printable. Click on the free curriculum link on the upper left hand side.
Macmillian/McGraw Hill offers online science activities for K-6th graders.
Robert Krampf's Science Experiments - great, quick videos of science experiments with explanations.
Houghton Mifflin Science has online flash activities for K-6.
BBC Science Clips - choose your child's age bracket on the left side. Great little interactive lessons!
Exploratorium - Great science experiments and online simulations
Middle School Science Experiements
Waterford Press - Science printables - animals, geology, natural sciences. Also origami animals.