Primary Sources
100 Documents that Shaped America
US National Archives & Records Administration
National Archives Digital Classroom - lots of ready-made resources and lesson plans
Political Cartoons
Dr. Suess Went to War - a collection of Suess’s political cartoons from WWII
General US History Sites
Library of Congress
American Memory - a sub-site of the Library of Congress
The Smithsonian
The Gilder Lehrman Institute of American History
The Constitution & Government
Interactive Constitution - from the National Constitution Center
The American Presidents
Regents Prep
Oswego City School District Regents Prep - This site has sections for all the exams, including US History. It includes practice multiple-choice, as well as essays.