A teacher friend of mine passed on this site and I love it! There are lots of linked interactive sites in various subject areas that can be used by students at home, in the classroom, or in the computer lab.
I use to like taking my students to the computer lab a couple of times during a unit to engage in science reviews via games and websites I had found. The children enjoyed the break and so did I :) Many of the students would play the games at home as well.
I explored the science section and it has a lot of great student friendly sites.