Hand, Eric. "Culturomics: Word Play." Nature 474(7352)(17 June 2011): 436-440. At: http://www.nature.com/news/2011/110617/full/474436a.html
This is an interesting article introducing Erez Lieberman Aiden, one of the developers of the n-grams viewer (a word frequency analysis tool) of Google Books. It has a nice sidebar describing some data mining projects in the humanities databases.