http://www.worldalmanacforkids.com/WAKI-Chapter.aspx?chapter_id=15
Government, US History, Historical Documents, Presidents, Wars, and States links.

http://www.census.gov/schools/facts/
Population, Geography, Business, History, and Trivia

http://www.stateanimals.com/
State animal, bird, amphibian, insect, butterfly, fresh water fish, and salt water fish.

http://www.kidskonnect.com/content/category/4/33/27/
Fast facts (when it became a state, area, population, major cities, products, climate, major waterways, and famous citizens), state symbols, and links.

http://www.ipl.org/div/kidspace/stateknow/
Facts, encyclopedia articles, state links, and famous people.

http://www.jewelrymall.com/stategems.html
State gems, minerals, rocks.

http://www.50states.com/
Dozens of categories each leading to other websites including: famous people, highest and lowest spots, state motto, cities, maps, and lots more