web sites

Wikipedia
This site defines transsexualism, and it gives information about the diagnosis, relation to gender roles, origins, relation to transgenderism, terminology, prevalence, causes, sex reassignment therapy, leagal and social aspects, coming out, regrets and detransitions, in the media, customs and transitions, and more.
It defines transsexualism like this: transsexualism is an individual’s identification with a gender inconsistent or not culturally associated with their biological sex. A medical diagnosis can be made if a person experiences discomfort as a result of a desire to be a member of the opposite se, or if a person experiences impaired functioning or distress as a result of that gender identification.
It might not be the best site, because anyone can revise and edit the information on this site, so it doesn’t have reliability.

"Transsexualism." Wikipedia, the free encyclopedia. Wikimedia Foundation, Inc., 11 may 2011. Web. 12 May 2011. .

Basic TG/ TS/ IS Information
by Lynn Conway
This site describes transsexualism very well.
It has three parts: Part 1 Gender Basics and Transgenderism, Part 2 Transsexualism, Part 3 Life as a Woman After TS Transition. Also it gives additional reference webpages such as TS Women’s Resources, TS Women’s Successes, Facial Feminization Surgery, TG/TS/IS Info Links, Successful TransMen, Sex Reassignment Surgery.
This site answers frequently asked questions, and it is very useful.
Conway, Lynn . "Basic TG/TS/IS ." Lynn's homepage. N.p., 26 05 2000. Web. 12 May 2011. .