The largest maritime museum in North America. The website provides valuable information on seafaring and oceanic voyages. The online image collection features over 2,000 images for personal or commercial use. Use this site as a primary resource for the study of explorers in Social Studies. Several biographies are given for explorers like John Cabot, Vasco Balboa, Magellan, and Amerigo Vespucci.
This site can be used as a resource for projects involving conservation, protection, or Nebraska ecosystems. If you study Nebraska animals or fish this is a great place to start. Every species of Nebraska fish can be viewed in detail using the fish identification tool, which also provides great descriptions and characteristics.
This website is a portal for many other websites that would be very useful for teaching. I haven't looked at all of the links, but there are links to major websites like the Smithsonian and Library of Congress, both of which I know have primary documents available on them. Not all of these sites have government documents on them, but many of them do.
This is another portal with a ton of great links. There is a page full of links for educators and then drop down menus that separate K-6 and 7-12. In these drop-down menus are links to entire pages of websites devoted to topics like the government, history, the military, math, and science. Not all of these sites have government documents, but many of them do.
I liked the educational direction this site provides for teachers. Besides the documents, this site provides lessons using the primary documents, and training on best practices for their use.