USGenWeb Archives table of contents is available at:
 
http://www.rootsweb.com/~usgenweb/
 
This provides links to their  archives by state. Each state listing is by
county. The project is just getting underway, but some counties have
entire 1850 or 1860 original census schedules, as well as Bible, letters,
obituaries, church records. In short, a good source for historical data.
I would hope that every historical archaeologist has similar data which
they could contribute to this site.
 
Another valuable web site is maintained by the Bureau of Land Management.
They are encoding the Government Land Office patents. One can search by
last name, or by location, and even download the original documents.
Their address is:
 
http://www.glorecords.blm.gov/