250 Killer Archives
http://oedb.org/library/features/250-plus-killer-digital-libraries-and-archives

Allen County Public Library
http://www.genealogycenter.org

Ancestry Card Catalog
http://www.ancestry.com/search/rectype/alldblist.aspx

Family Search Books
http://www.lib.byu.edu/fhc/index.php

Google Books
http://books.google.com

Hathi Trust
http://www.hathitrust.org

Internet Archive Texts
http://www.archive.org/details/texts

Internet Public Library
http://www.ipl.org

Library of Congress
http://www.loc.gov/index.html

Newberry Library
http://www.newberry.org

Open Library
http://openlibrary.org

PERSI
http://search.findmypast.com/search/periodical-source-index 

The Online Books Page
http://onlinebooks.library.upenn.edu/archives.html

WorldCat 
http://www.worldcat.org