http://ngrams.googlelabs.com/

The google nGram viewer lets you quickly and easily see the occurrence of a word, or words, across time as found in google books. Its visualization, like that of Facebook’s lexicon, take the form of a graph, with time as the x axis, and word frequency as the y axis. The scope of the nGram viewer is what makes it interesting — seeing how a word falls in and out of relevancy. As a tool it is straight forward, with no frills. While this makes the nGram viewer easy to use, the tool could benefit from easy ways to integrate “social” media. Why is there not a built in community, for example? While fun to play with, I’m not sure as a viewer that I want to sit there and spend time looking for a particularly insightful pairing of words to look up, and I would enjoy the opportunity of having a community built in to google that let me view graphs that others found interesting.

http://www.informationisbeautiful.net/visualizations/google-ngram-experiments/