Discover, experiment, invent, and explore as far as the galaxies here!
http://spaceplace.nasa.gov/ - NASA's Space Place has fun facts, activities, videos, pictures, quizzes, games, puzzles, and information about our solar system, the Sun, and outer space in general.
http://www.nasa.gov/audience/forkids/kidsclub/flash/index.html has interactive games about outer space and astronomy.
http://www.nasa.gov/audience/forstudents/k-4/index.html is NASA's educational site for kids, including games, NASA t.v., homework help, and more.
http://www.inventionatplay.org/ - There's lots you need to know about inventing here! Learn from real inventors, develop your creativity and innovation, practice your problem solving skills, imagine, and tinker around.
http://www.isek.iastate.edu/club/build-your-brain/brain-games/ - Engineers invent, design, test, repair, and improve inventions for us to use! Practice and develop your own engineering skills by playing fun games at this website!
http://www.howstuffworks.com/ - Satisfy (or wet) your curiosity at this website! Find out how things work here!
http://www.bbc.co.uk/science/humanbody/ - Be prepared to be grossed out or fascinated here! BBC's Human Body website has quizzes for you and lots of information about the human body. There are also links at the top of the page to BBC's sites about nature (wildlife, places, deadly animals), general science (such as astronomy), prehistoric life (you've got it!-dinosaurs), and space.
http://scifiles.larc.nasa.gov/kids/inside_treehouse.html - At NASA's SciFiles you can investigate real-life problems such as Ocean Currents, Technical Glitches, Suspicious Sickness, the Red Rover, the "Wright" Invention, Life on Mars, Puzzling Pyramids and more!