Not this crap again....
The Quran actually makes few references to homosexuality per se, and in the case of those few verses traditionally taken to refer to homosexual practices there is a wide variety of opinion as to what these verses actually mean, especially in more liberal circles.
The wording of my Bosnian Quran translation (don't have my English one to hand) talks of the 'sin of the people of Lot', a story which will be familiar to anyone who has similarly read the Bible. Traditionally this wording has been construed as referencing the sexual practices of the city, with reference to the men's refusal to take 'the daughters of the city' (i.e. taking a wife in marriage from among the women there, and not simply abusing Lot's daughters as the Bible puts it) and their desire to seize the male guests of Lot. However this is not explicitly explained to be the case, and more liberal Muslims argue that the primary crime of the men in the city was not their sexual practices, but their desire to dishonour the guest right by which the Angels were welcomed into Lot's home, offered food and drink and also a place of rest.
Some argue that this reading against homosexuality is backed by other Quran verses specifically referring to Islamic sexual relations. These verses typically only refer to sexual contact in the context of a valid marriage, between a man and a woman, who were created to be intended to be complimentary to one another and satisfy each other's needs (not just in terms of sex but more generally in terms of needs in life). I can't particularly discuss the merits of this as I don't know Arabic well enough to be able to comment on these.
The Quran however is not the sole source of Islamic beliefs and practices, and much of the controversies surrounding homosexuality in Islam stems from these. I have however not studied the issue in detail and so if anyone wishes to query this with me, I request they give me time to read up on this issue.
It must be said however there is no barrier for a gay man or woman to enter Islam, as long as they understand that to do so means celibacy. The key issue is that whilst homosexual thoughts are not in themselves particularly sinful or 'bad', acting upon them is a grave sin and control of lust (for both homo- and heterosexuals) is deemed to be a key virtue in Islam.
DISCLAIMER: As I have said once already, I don't know Arabic well and my Quranic knowledge is primarily based on my Bosnian translation. Similarly I do not credit myself as being in any way a trained scholar and what I have written is purely a personal understanding regarding the issue.