Some good history links

http://memory.loc.gov/ammem/collections/civil_war_maps/
Civil War Maps- Must see if you are a civil war buff or researching ancestors who were in the war between the states.
http://www.archives.gov/historical-docs/
America's Historic Documents

http://www.loc.gov/library/libarch-digital.html
main page for digital library from library of congress

http://www.loc.gov/chroniclingamerica/index.html
Online newspapers available for download

http://www.loc.gov/rr/print/catalog.html
Over 1 million digital images

http://lcweb2.loc.gov/diglib/lcwa/
websites that are no longer on the web live- archived- LOTS of stuff here.