ArchivingEarly America
http://www.earlyamerica.com/
Battlefield maps and other documents, mostly concerning the Revolution.

From Revolution to Reconstruction
http://grid.let.rug.nl/~welling/usa/usa.html
Includes a collection of political papers, with the Revolution heavily represented. Also some essays by amateur historians.

George Washington Papers
http://www.virginia.edu/~gwpapers/
Personal and political papers.

Letters From An American Farmer
http://xroads.virginia.edu/~HYPER/CREV/home.html
Crevecoeur's description of rural life in 1782.

Rare Map Collection - Revolutionary America
http://www.libs.uga.edu/darchive/hargrett/maps/revamer.html

The Benjamin Marston Diaries Project
http://www.lib.unb.ca/Texts/Marston/Marston.html The diary
of a Massachusetts Loyalist who fled to Canada.