I have a copy of the wonderful little book, The Joy of Pi by David Blatner, in my classroom and every day some student, be it a young geometer or an AP calculus ace, will take a look at it and then pass on to the class some interesting tidbit about pi.(See Convergence review of this book.) The author has developed a website, http://www.joyofpi.com, that is a great supplement to the book and includes many links that take the investigator to other sites that go into even more detail. The website is very easy to use and has two main parts: Pi Facts and Figures and Pi Links. Pi Facts and Figures has lots of information about pi, such as the many different ways that pi has been calculated over the years, its appearance in the visual and literary arts, attempts by a state legislature to redefine the value of pi to that given in the Bible (exactly 3!), just to mention a few. Pi Links contains an extensive, well annotated collection of web sites that you can use to find answers to almost any question you have about pi. I found only two links that didnt work out of over 50, so the list has been recently updated. There are links that can be used to supplement the teaching of all parts of the secondary curriculum. In my geometry class, we are about to begin a study of circles, and I am going to have each member of the class go to the site, find an interesting fact about pi not in the book, and report about what they find to the class. This comprehensive site is not fancy, is very easy to use and deserves to be included in all math teachers list of web favorites.
Jon Choate, Mathematics Dept., Groton School, Groton, MA