Conceptualizing sexual orientation
Terminology and concepts developed by Fritz Klein in his studies of bisexuality are extremely helpful in developing cross-divide discourse about sexual orientation. 

Using the Klein Scale to Teach  about Sexual Orientation  http://www.biresource.org/pamphlets/klein_graph.html  

"Sexual identity (how people think of themselves) sometimes has little to do with their sexual behavior."

NARTH: "Are Gays Born That Way?" http://www.narth.com/docs/bornway.html
"The best overall summary of most respected researchers is that  homosexuality (like most other psychological conditions) is due to a combination of social, biological, and psychological factors." The quote is from a  paper by NARTH which quotes from researchers in the field, researchers from both sides of the divide.   This paper is far more balanced than most NARTH papers and books which not only push a developmental theory, they also pathologize homosexuality. 

American  Psychiatric Association "Fact Sheet on Gay Lesbian and Bisexual Issues.    (a pdf file)

Page 5, Paragraph 2: "The validity, efficacy, and ethics of clinical attempts to change an individual's sexual orientation have been challenged.  To date there are no scientifically rigrous outcome studies to determine either the actual efficacy or harm of "reparative" treatments.  There is sparse scientific data about select criteria, risks versus benefits of the treatment, and long-term outcomes of "reparative' therapies.  The literature consists of anecdotal reports of individuals who have claimed to change, people who claim that attempts to change were harmful to them, and others who claimed to have changed and then later recanted those claims."

Page 4, excerpt from 1998 Position Statement.
"The American Psychiatric Association does not currently have a formal position statement on treatments that attempt to change a person's sexual orientation... there is no published evidence regarding the efficacy of "reparative therapy" ...  More importantly, altering sexual orientation is not an appropriate goal of psychiatric treatment... The American Psychiatric Associan opposes any psychiatric treatment, such as "reparative" or "conversion" therapy that is based on the assumption that homosexuality per se is based on a mental disorder, or based upon a prior assumption that a patient should change his/her sexual orientation."

American Psychological Association. Guidelines for Psychotherapy with Lesbian, Gay and Bisexual Clients

NARTH "We believe that clients have the right to claim a gay identity, or to diminish their homosexuality and to develop their heterosexual potential."  "NARTH agrees with the American Psychological Association that "biological, psychological and social factors" shape sexual identity at an early age for most people.  But the difference is one of emphasis. We place more emphasis on the psychological (family, peer and social) influences, while the American Psychological Association emphasizes biological influences--and has shown no interest in (indeed, a hostility toward) investigating those same psychological and social influences."

Finally Free: Personal Stories: How Love and Acceptance Saved us from "Ex-Gay" Ministries  
(pdf file) www.hrc.org/publications/exgay_ministries/FinallyFREE.pdf
Testimonies of ex-exgays, a publication of the Human Rights Campaign Foundation.

Mission Impossible: Why Reparative Therapies and Ex-Gay Ministries Fail
by Kim I. Mills, Education Director, Human Rights Campaign

A Third Way

2001 "Cures versus Choices: Agendas in Sexual Reorientation Therapy"
by A. Lee Beckstead, PhD
Abstract:  Longstanding debates have occured in the mental health fields on the issues surrounding sexual reoriantation therapy. Both sides agree that a subset of individuals with same-sex attraction seeks help or a "cure" for their homosexual attractions.  However, each position tends to respond with a limited, exclusionary choice to be an "out" gay or an "ex"-gay.  These dichotomized options may not serve all clients with same-sex attractions who are seeking help in dealing with religious conflicts.  The perspectives of 20 individuals (2 women, 18 men) who report benefiting from reparative/conversion therapy are described.  In contrast to previous imprecise claims of change, a more complex conceptual framework is presented regarding the definitions of a successful outcome from such treatments.  Research and political implications are discussed as well as the need for more effective clinical strategies that integrate conservative social identities with same-sex attractions   [Article copies available for a fee from The Haworth Document Delivery Sercice: 1-800-HAWORTH. Email address: <getinfo@haworthpressinc.com> Website: <http://www.HaworthPress.com>  2001 by the Haworth Press, Inc. All rights reserved.]
A short article by Lee Beckstead, summarizing his findings (written for an LDS audience)