I just want to make a distinction that there is a difference between what people believe as a part of their religion and the rights people receive as citizens who are a part of society. From a Christian perspective, there is the law you follow as part of your religion, and then from a secular perspective, there is the law that you follow in your society. I hold the opinion that someone's civil rights shouldn't be decided based on what the Bible says or doesn't say about sin... although there are certainly people out there who would have a word or two with me about that, I'm sure...
Sorry, Just being nit picky!
In terms of gay marriage, I would have to say that based on what little I know about the Bible, my impression would be that gay marriage is a no-no. However, in terms of gays getting married legally in our society, I don't give 2 ducks.
Here's a little gem of an article that offers some insight on what it is like to be gay and a christian:
Bible Translation Errors
You can also read about the author of the article, which is also an interesting read.
Hope this provides some useful or insightful information.