Here's what you'll need:
at least 1 disposable pizza pan (9" or bigger)
circle cutter (optional)
sweetened, condensed milk
The way in which we're going to commemorate π is with something I'm going to call a "pie circle". In other words, we're going to create a pie based on the design of a crop circle found in England in the middle of 2008. You can read all about that crop circle at this link:
Step 1: Start the Template
Cut an 8.5" circle from the center of the pizza pan. I used a circle cutter to "score" the rim of the circle, then a hobby knife to finish off any spots that weren't cut all the way through. Also cut the circle out of the graph paper; it should be about 8".
Tape the two circles together concentrically. I found it easier to cut the sections out of the template if I shaded in the parts to be cut first. Start by shading in the entire center two circles. Skip the next circle, then fill in three segments of the fourth circle, representing the 3 at the beginning of π. Skip the fifth circle, then fill in 1 segment, representing the 1 after the decimal. Continue in that fashion, skipping one circle between successive digits, until you hit the end of your graph paper. In my case, this was after the 9.