This is a collection of animated science storybooks for K-12 on a variety of topics ranging from electricity to Plate tectonics to the Rock Cycles and Life Cycles. The stories are fun, engaging and will be enjoyed by your science classes. You may even want to consider having your class create their own science stories. This is definitely one to add to your "go-to" collection!
This site offers a wealth of information for the science teacher or the teacher who has to teach science as part of their everyday curriculum. It includes resources as well as internet-based K-12 science lesson plans arranged by level and topic (K-2. 3-5, etc.). Honestly, it couldn't be any easier to find great online interactive science activities to go with your specific topic or theme. One other fun piece is the "Today in Science" feature. I think this site could be an amazing component of any classroom.
National Institute of Environmental Health Sciences
Games, puzzles and activity pages define this website. This link will take you directly to the index but if you click the home page you can access their environmental health activities, lessons and ideas of how to integrate the teaching into your curriculum.
This is the link to the vocabulary hangman games from Jefferson Lab. The topics range from seasons to animals, elements, biology, practically anything that you teach. There are also math vocabulary games for 5th-8th grade topics. My kids LOVE to play on this site to practice their science vocabulary. My 6th grader uses it to practice before science quizzes and tests. The great thing about this site is that YOU CAN UPLOAD your OWN vocabulary. So, if you have a topic that you are teaching in your class (ecosystems anyone) just upload your document of words and definitions and they will be added to the site.
It's National Geographic, it has everything you would think they have and more.
Missouri Botanical Garden (MBG Net)
This is a beautiful site with information and pictures about different habitats, ecosystems and biomes. Great for use when learning about the rainforest, temperate climates and more.