Astronomy for Kids: Explore the planets and other space related things learned in 3rd grade.
Jet Propulsion Lab site for Kids on Space: NASA
Colonial Williamsburg: History Site for Kids
Counting Money - Math Magician
Virtual Manipulatives: move things to learn about math.
International Children's Library: Read books here!
Uncle Ben's Web page about Government: by grade level!
Visual Math Learning and Games!
Math: Grades 4-6 Levels: MathFrog
Geometry: Cutting and manipulating shapes: Illuminations
Bio Cube: Create a biography (3rd grade or older) - helps you with organizing information about a person.
Write a Story and make a picture using Kerpoof
National Geographic Kids Page