Happy Pi Day! From Wikipedia:

Pi Dayis a holiday commemorating the mathematical constant π (pi). Pi Day is celebrated on March 14 (or 3/14 inmonth/daydate 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 Dayis held on July 22 (or 22/7 inday/monthdate 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.

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

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

I’m partial to Tau day myself. Not for any philosophical or mathematical reason, but because Tau day results in even better discounts 😀