Bookmarklets
This blog post from ResearchBuzz describes ways of searching for free and legitimate versions of news articles that are otherwise only found behind paywalls. Please note these techniques take a little time and do not find everything.
Chronicling America: Historic American Newspapers
US newspapers 1789-1963, digitised by the Library of Congress. Includes the US Newspaper Directory with information - not text - from a wider date range of US newspapers: 1690 to the present.
Europeana Newspapers
Digitised versions of newspapers from around Europe, from the seventeenth century onwards. 10 million pages in total.
Gallica: French newspapers
Good selection of historic French newspapers.
Global Press Archive
Digitised historic newspapers. A growing collection with worldwide coverage: particularly good for South and South-East Asia and the USA.
International News Archives on the Web
Not updated recently, but may be useful for finding news archives from particular countries.
Nigerian Newspapers
New project, initiated to digitise newspapers from 1960 onwards. As of October 2023, a range of editions from 1994-2010 are available.
Trove (Australian newspapers)
Search engine for material in Australian libraries, including newspapers. Tick the Available online box and run your search