Google, in partnership with a number of North American newspapers, ProQuest and Heritage, has begun digitizing printed newspapers, making them both searchable and browsable exactly as they appeared in print, including photographs, headlines, articles and advertisements.
From the official Google blog:
You’ll be able to explore this historical treasure trove by searching the Google News Archive or by using the timeline feature after searching Google News. Not every search will trigger this new content, but you can start by trying queries like [Nixon space shuttle] or [Titanic located]. Stories we’ve scanned under this initiative will appear alongside already-digitized material from publications like the New York Times as well as from archive aggregators, and are marked “Google News Archive.”
Here’s an example of an article about the first moon landing from a 1969 edition of the Pittsburgh Post-Gazette:
At some point in the future, Google plans to begin blending news archive results into main search results, in another expansion of its universal search initiative.
There are other newspaper archives available on the web, both free and fee-based. Journalism.net has an list of links to print newspaper archives online, including several non-North American sources in Europe, Asia, Africa and South America.