Check out the Illuminations site for fun Pi Day e-cards at http://illuminations.nctm.org/piday
We also have the lesson Apple Pi, http://illuminations.nctm.org/LessonDetail.aspx?ID=U159, Pi Filling, http://illuminations.nctm.org/LessonDetail.aspx?ID=U179 and our circle tool, http://illuminations.nctm.org/activitydetail.aspx?id=116 just to name a few.
I'm glad you started this discussion since Pi Day offers a chance to focus on math in a fun way. I think you would enjoy some of the ideas shared in a similar discussion posted for Pi Day 2011. Check out Pi Day in the Learning Math group. I especially like Wonder of the Day #162: What Is Pi? provided by Wonderopolis.
Thanks also for your link to some good resources.
Thanks, Lynn! Wonderopolis is quickly becoming my favorite TF partner. I love how the Pi post provides activities that can be used across the curriculum with reading, writing, and math using technology. It's also convenient that a sidebar links the user to TF, WonderFeed at Twitter, and all of the other Wonderopolis categories.
I just popped in on a Middle School math and science class. They baked pies this morning andt alked about the chemistry of baking in science. In math this afternoon the same kids had a Pi contest - seeing who could recite the digits of Pi to the farthest unit. The winners get to take home the pies from this morning!