Pi Minute is also sometimes celebrated on March 14 at 1:59 p.m. If [Pi] is truncated to seven decimal places, it becomes 3.1415926, making March 14 at 1:59:26 p.m., Pi Second (or sometimes March 14, 1592 at 6:53:58 a.m.).
The first Pi Day celebration was held at the San Francisco Exploratorium in 1988, with staff and public marching around one of its circular spaces, and then consuming fruit pies; the museum has since added pizza pies to its Pi Day menu. The founder of Pi Day was Larry Shaw, a now retired physicist at the Exploratorium who still helps out with the celebrations.
This year it is officially National Pi day too, according to the U.S. Congress!
Be sure to do some pi-ous things, ok? (Making pies, walking in circles at 1:59 pm (at the 26th second), and so forth… [Update: You can hear more about what to do by listening to this 2004 K C Cole commentary about the day.]
Some other ideas can be obtained from the official site. (And yes, you can study how physicists are supposed to talk – no, no, not really! – for Talk Like a Physicist Day here. Ok, although I somewhat resist going too far with the notion that we physicists are abnormal, my concession might be to have an amusing physics inspired facebook status for some of today. Amusing, I said, so not most of those here. 🙂 )