Enchanted Learning http://www.enchantedlearning.com
National Geographic for Kids http://www.nationalgeographic.com/kids/
Exploratorium http://www.exploratorium.edu/
Nasa Kids http://solarsystem.nasa.gov/kids/nasakids.cfm
Smithsonian Education http://www.smithsonianeducation.org/students/
Matter http://www.harcourtschool.com/activity/states_of_matter/index.html
The Great Plant Escape Parts of a plant and why each part is important http://www.urbanext.uiuc.edu/gpe/gpe.html
Exploring the Secret Life of Trees http://www.urbanext.uiuc.edu/trees2/
Biology of Plants http://mbgnet.mobot.org/bioplants/main.html