Crash Course US History --a great series containing 48 episodes based of the AP US History Curriculum.
Mr. Betts Class--Videos on various history topics...some are quite funny!
Khan Academy US History Course --great resource with lecture/documentary style videos taking you through a chronological timeline of American history.
U.S. History Free Online Text --a bit more detailed and similar to a traditional text book
American History for Kids --engaging and easy to read resource.
Epic History TV --Eurocentric version of World History but touches upon some American History topics
Hip Hughes U.S. History Explained --highly engaging and entertaining video series created by an AP US History teacher
History.com --if it is historical chances are the History Channel has it covered in some way.
Woods Runner by Gary Paulsen --one of my favorites...a historical fiction text highlighting the effects of the Revolutionary War on a boy and his family.
Mission US For Crown or Colony --interactive game that takes its players through historical situations...even includes primary source documents one has to read in order to complete the game.