A few other sites worth looking into:
Uclue...a Q&A site founded by a number of former Google Answers researchers. A great place for low-cost, high-quality research work, with research starting at only $10.
Archaeolink.com...for information on anything and everything related to archaeology and anthropology.
FirstMention...where you can explore the history, origins and earliest appearance of common words, phrases, names, events, and places.
Newspaper Archives for Free...find old newspaper headlines, articles, advertisements, editorials on historical eents both large and small.
How To...A series of short, helpful articles on everything from writing well, to getting free information from Lexis-Nexis, and Dun & Bradstreet.
See XooxleAnswers' write-up on newspaper archives at eHow.com