Gagnon

Dr. Robert Gagnon serves as associate professor of New Testament at Pittsburg Theological Seminary.  He's written a key scholarly work regarding biblical truth and the homosexual discussion, The Bible and Homosexual Practice: Texts and Hermeneutics, and contributed to the work, Homosexuality and the Bible: Two Views.  Check out his site, http://www.robgagnon.net/, which has many useful articles and responses to common homosexual arguments. 

LaBarbera

Peter LaBarbera is president of Americans for Truth.  His site www.americansfortruth.com provides another useful place where you can find information to refute common arguments from the gay rights movement. (Note: It comes with a caution that his site contains material not suitable for children.)