Without the Exploratorium, we might never have had an official Pi Day celebration. In 1988 Exploratorium physicist Larry Shaw started the tradition, and it was finally recognized by Congress in 2009. The Exploratorium highlights some great hands-on activities, and there is also a great list of Pi-related links.
If you want to expand your way of thinking and your knowledge of the universe and take a look at the science of the world from a non-Christian point of view, READ THIS. It's totally stretching my mind.
23 Books Facebook CEO Mark Zuckerberg Recommends You Read