Intersex Society of North America
This is the homepage of the Intersex Society of North America. While the organization no longer exists, Eugenides mentions it a couple of times within the novel. The website contains a good Frequently Asked Questions section, addressing what it means to be intersex, and has, according to the message on the front page, been left up as "an historical artifact."
Jeffrey Eugenides' Professor Page
http://www.princeton.edu/arts/arts_at_princeton/creative_writing/professor_bios/eugenides/
Jeffrey Eugenides is a professor of Creative Writing at Princeton University, and this page contains basic information about his background and interests, as well as contact information.
NPR Collection of Jeffrey Eugenides
http://www.npr.org/books/authors/138256010/jeffrey-eugenides
This link leads you to a collection of material NPR has published on Jeffrey Eugenides including interviews, reviews, and excerpts of other material.