Two of many lessons at Illuminations:

Pi Line - Lesson Plan - students will measure the diameter and circumference of various circular objects, plot the measurements on a graph, and relate the slope of the line to π, the ratio of circumference to diameter.

Apple Pi - Lesson Plan - Using estimation and measurement skills, students will determine the ratio of circumference to diameter and explore the meaning of π. Students will discover the circumference and area formulas based on their investigations.

Math Forum - a list of many different types of Pi Day Activities

From the Math Forum - Making a Pi Necklace - As a 7th grade math teacher, this teacher likes to make mathematics as visual as possible. For Pi Day, her students make Pi necklaces.

Mr Herte's Pi Day - Pi Day is a day to celebrate mathematics in your school. It gives us the perfect springboard to allow students to have fun while investigating mathematics concepts, being creative and even a little silly. If you have any ideas email them to Mr. Herte.

Mr Herte's Pi Day Song

Teach Pi.org one-stop Pi Day shop for teachers and number lovers. This organization believes that promoting an enthusiasm for learning, through celebration and creativity, will lead only to a richer classroom environment and a deeper appreciation of mathematics.

Plan a Pi Day Party for March 14 - If one day of the year screams Party! in math class, that day is March 14. Each year on 3/14, teachers in classrooms across the globe take a break from the normal routine to plan a special celebration in honor of pi, or the number 3.14...