π Day (Pi Day) is upon us soon (on 3/14 or March 14). If you'd like to prepare for it and have some activities for your children/students, check these resources.
If your students don't yet know what Pi is, start with the basics: it is very fitting to explain and discover pi on Pi Day.
Here's a Pi webquest for older students who can search the Internet and encyclopedias on their own. The "Historian" in the webquest has to find answers to some questions, while the "Pi Maker" needs to make an edible model that shows the parts of a circle necessary in finding the value of pi.
BrainPop has a movie about Pi.
Remember also that 22/7 is a great fractional approximation to Pi. This means that if 7 pepperonis nicely fit in the diameter of a pizza, then 22 nicely fit to go around.
(From Exploratorium.edu Pi posters)
Find where your birthday is in Pi - e.g. if your birthday is March 14, 1971, find where in Pi's digits is the sequence 31471. (Mine wasn't anywhere in the digits it searched.)
You can read how other teachers have celebrated Pi day. Lots of them use pies - mmmm!
2009 21st Annual Pi Day Celebration page is a good place to spend some time on Pi day or otherwise. You can see read history of Pi, see previous Pi Day images, read Pi limericks, download Pi posters and so on.
Then once you are done with that and STILL have appetite for more, go explore tons more Pi stuff at the links found here.