I hope you'll read my letter to the Catholic Church about why I want to be excommunicated:

Today, Bishop Malone, I am demanding that you excommunicate me. I cannot in good conscience belong to your church anymore; I do not want to be counted with the 200,000 Catholics in Maine, or the 68,115,001 Catholics in the United States of America, or the 1.1 billion Catholics in the world.

And if you want to demand excommunication, I wrote a quick-and-dirty guide for you:

When people ask you about your religion at parties, you refer to yourself as a "recovering Catholic," but you never gave your baptism or confirmation much thought beyond that. Now, though, you've had it. You're tired of waiting for Pope Ratzi to hang up his funny- shaped hat, and you're tired of being associated with the moral monstrosity that is the Catholic Church. You need to excommunicate yourself! It's a relatively easy thing to do, and though the Catholic Church still considers excommunicated people to be Catholics—albeit of the "unforgiven" variety—you can at least take comfort that you've removed yourself as far as humanly possible from an organization you detest.