A friend posted this link on Facebook.
Elephind – over 2,000 newspaper titles representing 2 million newspapers and 55 million articles/pages from Australia, Mexico, New Zealand, Singapore, and the United States. Ran a quick search and it included Trove and Chronicling America results.
Old Fulton New York Post Cards – more than 26.1 million pages of New York newspapers. One of the best sources for New York state newspapers.
Chronicling America/Library of Congress – over 7.246 million pages from 36 U.S. states.
Google News Archive – more than 2,500 newspapers.
The link does not mention NewspaperArchive.com which offers one free page view/day if you use your Facebook account to log-in. They used to offer 10 free page views/day, but they reduced it to one a while back. A nice thing about NewspaperArchive is you can do multiple searches before using your one free page view. The searches usually give you a brief snippet of the article which is helpful in determining if it is relevant.
Another source of potentially free Internet newspapers is your local public library, historical/genealogical society, or college. In some cases, the access is only available on-site. For example, Wichita Public Library system allows off-site access to Newsbank articles from the local newspaper. If you are a member of certain societies, libraries, or museums, you may get access to online newspapers as a member benefit. You may have to access the resource on-site, but several offer off-site access.
Wikipedia has a list of online newspapers, both free and paid.