Some know pi to another couple of digits as 3.1415, which is why the 2015 occurrence of Pi Day is especially significant. To commemorate the occasion, you are invited to attend a flashmob event on March 14/15, from 9:15am to 9:45am at the posted coordinates.
To take the concept one step further and commemorate the occasion, we will be taking a photo of all who are present at precisely 9:26:53am, which will recognize pi to 9 decimal places! (3.141592653) How geeky is that?
There will be a few surprises, and Groundspeak has indicated that there will be a virtual souvenir added to your profile if you attend an event on this date. Hope to see you there!
We took a couple of pictures to commemorate the event. In this first photo, the attendees formed the pi symbol, which would have been a lot more impressive if we had been able to take the picture from higher up to get the full effect! 
In this second shot, the attendees formed pi to 11 digits, lining up in columns of 3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5 and three more crouching to form the ellipsis. A big "thank you" to MrsS for scaling the hill to take the picture, and to Bear the geodog for forming the decimal point!
And an especially big "thank you" to all of the attendees for coming out on a colder-and-rainier-than-expected morning for the event! Now go find yourselves a puzzle cache; you've earned it!