Me, there are some great references in the above posts, but if you want one more, there is a book by a conservative gay Christian, called Torn. It is by Justin Lee. It is well worth reading. He also created an online Gay Christian Network called http://www.gaychristian.net/
if you want to find Biblical support. I am a progressive Christian, so I'm not much help otherwise. My saying is "If they are telling you that you need to change, what you need to change is your church."
Another really good book is Gay By God, by Michael Piazza. Both books dig into the myth that the Bible says it is wrong to be gay.
I suggest you check out the books, videos and links so you can start arming yourself with responses. Then hand your parents a few of the things you have read and learned and watched. Tell them you will not have a conversation with them until they have read the books, watched the videos and attended at least 2 PFLAG meetings with you. Then the conversation can begin.
And don't forget that we are all here for support if you ever need it.