Many projects require some research depth into events in the past. Newspapers are good sources for such research as they report on events-of-the-day and often include primary source material.
We’ve added these resources to the deep web search engines page
Deep Web Newspaper Archives Online
US newspaper coverage – ResearchGuides lists links to many newspapers
Library of Congress Newspaper Resource List – LOC does a great job getting the list together of wonderful newspaper archives.
NewspaperArchive.com – (commercial) – Known for a large collection. I haven’t used it, so I can’t confirm this.
xooxleanswers.com – Great list of newspaper archives from Xooxle. Good list and a funky name. Two thumbs up.
University of Penn Newspaper Archive – List of US newspaper archives and dates. Looked like a deeper list of Texas newspapers, so this effort may be a deep comprehensive list.