Another very good definition from About That X blog:

"Intersex can be defined as one who is born with genitalia and/or secondary sex characteristics determined as neither exclusively male nor female, or which combine features of the male and female sexes.Lately there has been a move to drop the term "intersex" in medical usage, replacing it with "Disorders of Sex Development" (DSD) in order to avoid conflating anatomy with identity. However, this has been met with criticism from some activists who consider intersex to be a third gender. The phrase "ambiguous genitalia" refers specifically to genital appearance, but not all intersex conditions result in atypical genital appearance."

Intersex/47,XXY Blog - Xnister Xnister says this is "my take on the anomaly that is XXY, my views may differ from what you have learned thus far, but then, aren't we, who are XXY, also just that little bit different?

Intersex Initiative

Organisation Internationale des Intersexués is "Dedicated to the Advancement and Diffusion of Knowledge and Understanding of Gender./ Consacré à la promotion et la diffusion des connaissances sur les questions de genre." The site has information in several languages: French, English, Spanish and Dutch.

Press for Change is a political lobbying and educational organization that campaigns to achieve equal civil rights and liberties for all transgendered people in the United Kingdom, through legislation and social change.  This is a very large and extensive site and well worth checking out.  Though it is a U.K. organization much of the site information is universal.