Another tiered science website with beginning, intermediate, and advanced levels. It covers three main topics: our planet, our solar system, and our universe. There is a TON of information on this site...I'm sure you could connect it to something you are learning in science!
All sorts of math, science, and lanuage arts activities that can be used on the smartboard. There are science activities for the food chain, health and growth, plants and animals and much more. 4th grade - there is a an activity for friction and forces in motion that made a great formative acitivity last year.
This is a great website if you do anything with the human body. I know 5th grade has a whole science unit on it, but didn't know if anyone else might be able to use it, too!
Leveled reading for learning about astronomy. Sponsored by NASA and has a lot of good information if you have a child interested in this topic or you are studying this in a content area.