Tennessee Valley Authority
In 1933, President Franklin Roosevelt initiated a new agency which combined aspects of governmental and private organizations. Over time, the resulting agency, the Tennessee Valley Authority or TVA, has researched issues as far-ranging as malaria, reforestation, power, flooding, navigation, and erosion. In their own words, the TVA serves the "valley through energy, environment, and economic development."
Admittedly, the TVA website was not designed for K-12 education. However, as a major initiative of the New Deal, it is an important milestone in U.S. history. For that reason, if you need to teach the New Deal, you may want to read From the New Deal to the a New Century: A Short History of TVA, which includes a link to the original TVA Act. The TVA Heritage archive focuses on more specific snippets of TVA history.
Also worth a look is the TVA kids' site, which includes answers to questions like "Who developed the Cherokee alphabet?" and "In 1930, how many Americans living on farms had electricity?" Resources specifically developed for teachers lean toward the sciences.