A site aimed towards the primary years. Used this during my internship in a kindergarten classroom. Not only did the kids love it, they were able to interact with many of the aspects during the free time on one of the PCs in the classroom, or during the morning circle on the SMART board.
A great resource for lesson plans that is aesthetically pleasing and easy to navigate. I've used it during my time as an undergraduate student, and found it very helpful.
An intruiging search engine provided by google that allows you to search for one topic (ex: fractions) and gives you books, translations, videos, 3D explorations and more.