Google News Archives
The Best of the Best
Update: Google News Archives is changing rapidly. Google is not only responding to newly available sources, but is also being challenged by a variety of lawsuits and industry pressure about what it can and can't publish as archived materials. The description that follows will no doubt be out of date by the time you read it (if you read it). But do check out Google's archives, as well as the other archives, historical resources and family-history tools I've linked to at the bottom of the page.
Google (big surprise!) heads the list with its wonderful Google News Archive Search.
I suspect even a lot of folks who are familiar with Google News (which covers the past year or so of news) may not know about the full depth of resources available at their News Archives. The files here go back to the 1700's. By combining results from numerous, deep, independent archives -- and allowing searches to occur at Google speed -- this is usually the first place I stop for any broad-based historical searching.
Search results can be one big list, or can be sorted into a Timeline, so you can quickly access all the stories from, say, the 1850's. And of course, the Advanced Search functions allow you to fine tune the results even further.
Google News Archives provides content from dozens of different sources, which is both a strength and a weakness. Clicking on a particular search result may lead you to the full article, or it may just lead you to a log-in page, telling you how much it costs to access the article text.
New Google now (finally!) has a full list of archived newspapers and other news sources -- more than 2,400 sources in all. Names and dates are shown, from A Propos (1973-1974) to the Youngstown Evening Vindicator (1891-1893). But inexplicably, Google makes no mention of where the publication is from.
Multiple sources also make for a mixed bag of results...there's a fair amount of chaff mixed in with the wheat, if you catch my meaning. After a while, you get a bit familiar with the quality of the sources, and learn to start ignoring the ones that need ignoring.
Google isn't the only game in town, however. One of the best archives available is the aptly-named NewspaperArchive.com
. This is a subscription service, but well worth it. I use them constantly in my research, and recommend them highly.
There are plenty more archives, historical sources, people-find tools and family history research resources worth knowing about:
Court Record Searches
Public Records Searches 
Online State Archives