Often times people will tell you that the Bible clearly opposes homosexuality and this is made clear in the story of Sodom and Gomorrah. This story is found in the book of Genesis and tells of the inhabitants of the towns of Sodom and Gomorrah who were destroyed for their sinful ways.
One passage, Genesis 19:5 says, "And they called unto Lot, and said unto him, Where are the men which came in to thee this night? Bring them out unto us, that we may know them."
People usually interpret the the word "know" as meaning "to have sex with." Some people claim that the people of Sodom and Gomorrah were punished because the men of the town "knew" other men.
However, others believe that it was not gay sex that got the town in trouble, but rape. This interpretation is strengthen by the fact that nowhere in Genesis is "homosexuality" mentioned. Interpreting this one passage as being a discussion of homosexuality is often seen as a limited view. Read more about that on Gay Christian 101.