Pi Day (3/14) is a big holiday for a big nerd like me, no less because in robotics it was one of the most celebrated holidays of the year. In fact, we not only ate pies on Pi Day, we spent the whole school day, in shifts of course, writing the digits of pi in chalk along the all-outdoor hallways. We even had a map to delegate where people should write their digits so that they were most efficiently spaced out. If I remember correctly, we got up to 7,000 digits (verified by Slice of Pink's entry from one year). I also memorized the first 25 digits of pi due to said chalk-writing and I believe to win a bet with a friend.
The digits of pi have my former robotics team number "399" pretty early on in the sequence so it was clearly our obligation to spread the word about the beauty of pi. This website has 1 million digits of pi listed, if you were ever interested in knowing them to that degree. And this mug is something that I think someone should buy me in honor of Pi Day, my 21st birthday, Easter, or any other excuse they can think of.