Today is 3-14, otherwise known as Pi Day. That means we plan to expand our waistlines exponentially and celebrate the numerically sweet quasi-holiday with a hulking slice of pie! Where should we go?

First it's off to Morton's, whose Back Bay and Seaport locations offer a distinctly spring-like Key Lime pie for $3.14. Not surprisingly, Harvard math major Joanne Chang has Flour bakery in on the action, with a special chocolate creme pie on offer at all three locations. Then we'll hustle over to Petsi Pies by 1:59 p.m. At this precise minute, they'll give away mini-pies. (For those who failed high school math, Pi=3.14159 ... we think.) MIT folks should note that if you visit Petsi's and recite ten digits of pi, you'll receive a free mini pie. Reciting 25 digits will earn you a Petsi gift certificate. And, if you're feeling really *Rain Man*-esque, recite 50 or 100 digits and win a gift certificate to Petsi Pies *and* their sister Tupelo restaurant. It's really a shame that Pie Bakery closed!