Wedding Crunchers: An n-gram analysis of wedding announcements in the New York Times going back to 1981. See, for example, the decline in elite prep schools, how well the five boroughs are represented, or the rise (and fall) of hedge fund managers among the newly wed. The site's creator offers a more detailed look over at Rap Genius.
The Music Ngram Viewer from Peachnote tracks appearances of any given note or chord sequence in a corpus of 60,000 optically scanned public-domain classical scores, ranging from the 17th century to the present -- a la what Google Ngram Viewer does for words and phrases. A fuller description with examples. And if you don't like the Google-esque GUI, you can download the raw data and mess with it yourself. (Via Music Hack Day Boston.)
Google's new Ngram Viewer lets you track the history of words in six languages, including several flavo(u)rs of English. Whether it's the rise and fall of a single word, the evolution of technology, or the mysterious seventeenth-century proliferation of fart jokes, there's a lot to play with. More at the Official Google Blog.