This site allows students to explore land & water management, national parks, minerals, fish & wildlife in the US. Check out the Astrogeology link for exploring our planetary system.
A subsearch of National Geographic. If you are looking for primary source photographs, these are beautiful. They have a direct link for downloading photos to Diigo. Many categories of photos. This particular site on rainforests would be useful to elementary school students doing research on environments, animal habitats, etc.
The WorldWildlifeFund has long been a reliable and strong force in global efforts to protect some of our worlds most vulnerable animals. Though the site solicits donations, the articles on animals and facts about endangerment are great resources for students doing animal research. Beautiful photos and facts.