ABC Science is a basic science website for all ages and includes articles, quizzes and games for all topics in science.
Kids.gov has articles, games and videos on topics including earth science, chemistry, life science, physics and space for students in grades 6-8.
Science News has has interesting news articles and resources for hands-on activities and books to read in atoms and forces, earth and sky, humans and health, life, and technology and math.
neok12 has educational videos, lessons and games for k-12 students in topics including physical science, life science, earth and space and human body.
Exploratorium is a great tool for students to learn more about science in general. This website has articles, videos and things to do in topics such as astronomy and space, earth, everyday science, living things, material world, mind and seeing.
ARKive is an educational tool for students and teachers alike to learn about all species of animals on Earth- extinct or extant (still living).
DragonflyTV is an educational website made by PBS which is based on science. Here, you can find information on real scientists, experiments at home, games, riddles, puzzles, and ideas for the science fair.