Happy Pi Day! From Wikipedia:

Pi Day is a holiday commemorating the mathematical constant π (pi). Pi Day is celebrated on March 14 (or 3/14 in month/day date format), since 3, 1 and 4 are the three most significant digits of π in the decimal form. In 2009, the United States House of Representatives supported the designation of Pi Day.

Pi Approximation Day is held on July 22 (or 22/7 in day/month date format), since the fraction ²²⁄₇ is a common approximation of π.

Larry Shaw created Pi Day in 1988. The holiday was celebrated at the San Francisco Exploratorium, where Shaw worked as a physicist, with staff and public marching around one of its circular spaces, then consuming fruit pies.

The Exploratorium in San Francisco has Pi Day 2012 programming in celebration of everyone’s favorite math constant.

In celebration of Pi Day, Adafruit is offering 3.1415% off everything in the store! Check out with code “pi” for the discount, valid through 11:59pm 3/14/2012.

Pi Day on Dinosaur Comics

Big Fluff Pi (plush Big Muff Pi pedal)

Pi pie trivet by Evil Mad Scientist Laboratories

Sterling silver Pi earrings on by Nicholas and Felice

Radian chocolate pudding pi

Candy Pi calculator

Handy Pi divider tool (measure the diameter with the calipers and the other end displays the circumference).

Pi scarf

How to install a Pi tile backsplash