Have you ever wondered what types of math are trending (more popular) now, other than when Pythagoras was still alive. Now you can at http://books.google.com/ngrams . Ngrams is a viewer in google which takes words or phrases in which particular words appear.
Now if you were thinking about the Pythagorean theorem for example:
the following ngram shows that it didn't start gaining popularity and reach its peak in the 1990's. Now it is being used by scientists and mathematicians all over the world.
The ngram viewer takes history at its most rote and transforms all the history you know in to one small graph about it. That's incredibly powerful. Ngrams are going to change the way teachers teach math, history, language arts, and every other core subject. It's a gamechanger!