Most of these transgender research articles have been published in scholarly, peer-reviewed journals (obviously, the Wikipedia entries on bottom do not count):
Combined Gender Identity and Sexuality Inventory (COGIATI) — this measures your level of transsexual:
http://transsexual.org/cogiati_english.html
Basic Transgender/Transsexual/Intersex Information, by Lynn Conway, a Professor of Electrical Engineering and Computer Science at University of Michigan:
http://ai.eecs.umich.edu/people/conway/TS/TS.html
Erotical Illusions, A Google TechTalk, by Ogi Ogas (he explains why men love transgender individuals so much):
http://www.youtube.com/watch?v=p-A8GvUehq4
Turning Lemons into Lemonade: Hardiness Helps People Turn Stressful Circumstances into Opportunities, by The American Psychological Association (this isn’t really about transgender issues, but I feel that it’s helpful nonetheless):
http://www.apa.org/research/action/lemon.aspx
Blanchard’s Transsexualism Typology (Wikipedia Entry):
http://en.wikipedia.org/wiki/Blanchard%27s_transsexualism_typology
The Story of David Reimer (Wikipedia Entry):
http://en.wikipedia.org/wiki/David_Reimer