Transsexuals, transgendered people, cross-dressers, and others redefining gender.
Counting Past Two
http://www.countingpast2.com
Web site of an annual transsexual/transgender cultural festival in Toronto. And beautifully designed, if we don't say so ourselves! ;-)
Gender and Transgender Theory
http://www.bcholmes.org/tg/
A site by the very fascinating B.C. Holmes, with insightful articles on the relationship between gender and spiritualty, postmodernism, and many other things.
GenderWeb
http://www.genderweb.org/
Articles, discussion forums, mailing lists, and other resources by, for or about transsexuals. I especially liked "20 Things You DON'T Say to a Transsexual" ("DON'T #18 - 'Well, I want you to know I respect your choices.' And I yours, particularly in transcendent matters, such as whether to register your pattern at Bloomingdale's or Saks, or whether a bright, robust yet tart, Almanden can properly accompany sushi.")
Transgender Forum
http://www.tgforum.com/
A large and comprehensive site with live chat, discussion forums, webmail, personal ads, a resource guide, and an e-zine. Most of it is available only through a paid membership but there is some free content too.