Another great resource for science is the NASA Wavelength site. I love the resources NASA provides to educators, and have some older posts on the NASA digital learning network. The Wavelength site has hundreds of free resources and lessons at all levels (626 at the Elementary level alone!) by providing links to external sights. Two that caught my eye right away were introducing temperature measurement for primary grades and The Mystery of the Missing Hummingbirds. Please try out this fabulous science resource.