You can also go to Google News at http://news.google.com/nwshp
and click on the arrow in the search bar for Advanced News Search. A form pops up and where it says "Date added to Google News:" you click in the box that says "anytime" as the default and change it to "in archive". Some of the hits will be free and some will show a price but if you click on them they will have a free excerpt.
You can also go directly to the newspaper news archive search page at http://news.google.com/newspapers
if you know the name of the paper you want to search or if you just want to browse. A lot of newspapers, though, to browse.
They say they are not adding new newspapers but don't say anything about removing any content.