100 Milestone documents from our history
http://www.ourdocuments.gov/content.php?page=milestone

Library of Congress American Memory
http://memory.loc.gov/ammem/

Famous Speeches from the History Channel
http://www.historychannel.com/speeches/archive1.html

Civil War Era
http://scriptorium.lib.duke.edu/women/cwdocs.html

WWI
http://www.gwpda.org

Presidential Libraries
T. Roosevelt   http://www.theodoreroosevelt.org/modern/harvardcol.htm
F. Roosevelt   http://www.fdrlibrary.marist.edu/
Truman          http://www.trumanlibrary.org/
Eisenhower    http://www.eisenhower.archives.gob/D1/hd.htm
Kennedy        http://www.jfklibrary.org/archives/htm
Nixon             http://www.nixonfoundation.org/Research_Center/PublicPapers.cfm
Ford               http://www.ford.utexas.edu
Carter            http://www.jimmycarterlibrary.org/library/
Reagan          http://www.reaganfoundation.org/visitorguide/about_rlibrary.asp
Bush             http://bushlibrary.tamu.edu/
Clinton          http://www.clintonlibrary.gov/
 

Avalon Project - Documents in Law, History and Diplomacy
http://avalon.law.yale.edu/subject_menus/nazsov.asp

Repositories of Primary Sources in US
http://www.uidaho.edu/special-collections/Other.Repositories.html