just to clarify female circumcision predates islam and isn't practiced by the majority of muslims and isn't required by the qur'an
some good info here
http://en.wikipedia.org/wiki/Female_circumcision
including info on where female circumcision has been practiced or advocated, other religions etc
including on christianity
"Christianity
As the FGC rituals predated the missionaries work in North Africa, many African tribes continue the practice as a matter of tradition, despite their religious conversion. In primarily Christian countries (for instance, Ghana), women undergoing circumcision make reference to the practice in the Old Testament, being performed by Abraham's wife, Sarah. However Genesis 17:23-27 only mentions circumcision being performed on male members of the household, and not on Sarah.
In the United States, as recently as 1938, FGC was advocated by some Christian evangelists as a method of preventing masturbation. As one Methodist preacher prescribed: "While incest and illicit commerce of the sexes is abominable, there is another even more so--if that be possible--that is, the heinous sin of self-pollution or masturbation.... In some cases where there may be impingment of the clitoris, a slight operation may be necessary to relieve the tension and irritation...." [36]"