I Corinthians 6:9 says the "effeminate" and "homosexuals" will not inherit the kingdom of God.
The word used here for effeminate is malakos in Greek and homosexual is arsenokoitai.
Some trying to explain away these words by pointing out that when malakos is used as a phrase with cloths means "soft cloths" and therefore has nothing to do with homosexuality. That is like saying "gay" means happy and therefore has nothing to do with homosexuality. (Not in this culture)

The following are secular references where the word malakos is used of certain people (namely catamites) the description of which can be nothing other than homosexuality.

Dionys. Hal. 7, 2, 4; Dio Chrys. 49[66], 25; Ptolem., PHib. 54, 11 [c.245 BC] 

The following are secular references where the word arsenokoitai is used of a male who practices homosexuality, pederast, sodomite.

Bardesanes in Euseb., Pr. Ev. 6, 10, 25 - Anth. Pal. 9, 686, 5 and Cat. Cod. Astr. VIII 4 p. 196, 6; 8; Sib. Or. 2,73

Romans 1:26,27 describes homosexuality as "degrading their bodies" by "women exchanging the natural relations for unnatural ones" and "men abandoning natural relations with women and were inflamed with lust one for the other." "Men committed indecent acts with other men, and received in themselves the due penalty of their perversion." and this is called "degrading, unnatural, vile affection, indecent, depraved, and an error." 

Some try to say that this is a purity law out of the old testament, and therefore does not apply to Christians. Anything Paul says is sin in the new testament, whether it is in the old testament purity code or not, it must be considered a moral sin, and therefore binding on Christians today.

Early Church Fathers:
The following first and second century church fathers described the sin of homosexuality.

1. You shall not commit adultery; you shall not commit pederasty. Didache 2.2 (c. 80-140).
2. It is well that they should be cut off from the lusts of the world, since “every lust wars against the spirit’ and “neither fornicators, nor homosexual... will inherit the kingdom of God.” Clement of Rome (c. 96), ECF 1.34.
3. Some polluted themselves by lying with males. Aristides (Syriac version) 8 (c. 125).
4. The Greeks, O King, follow debased practices in intercourse with males, or with mothers, sisters and daughters. Yet, they, in turn, impute their monstrous impurity to the Christians. Aristides (Syriac version) 17 (c. 125).
5. Pederasty is condemned by the barbarians. However, by the Romans it is honored with certain privileges. In fact, they try to collect herds of boys like grazing horses. Tatian, Greeks 28 (c. 160).
6. They do not abstain even from males, males with males committing shocking abominations, outraging all the noblest and comeliest bodies in all sorts of ways. Athenagoras (c. 175) ECF 2.143
7. Show me yourself whether you are not an adulterer, a fornicator, a thief, a robber. Show me that you do not corrupt boys.  ...For God is not manifest to those who do these things, Theophilus 1.2 (c. 180).
8. Men play the part or women and women that of men, contrary to nature. Women are at once both wives and husbands... O miserable spectacle! Horrible conduct! Clement of Alexandria, Instructor 3.4 (c. 195).
9. The whole earth has now become full of fornication and wickedness. I admire the ancient legislators of the Romans. These men detested effeminacy of conduct. The giving of the body to feminine purposes, contrary to the law of nature, they judged worthy of the most extreme penalty. Clement of Alexandria (c. 195) ECF 2.77
10. The fate of the Sodomites was judgment to those who had done wrong, and instruction to those who hear. The Sodomites had fallen into uncleanness through much luxury. They practiced adultery shamelessly, and they burned with insane love for boys. Clement of Alexandria, Instructor 3.10 (c. 195).
11. The Christian man confines himself to the female sex. Tertullian (c. 197) ECF 3.51.
12. I find no dress cursed by God except a woman’s dress on a man. For he says, “Cursed is every man who clothes himself in woman’s attire.” Tertullian (c. 200) ECF 3.71.
13. The coupling of two males is a very shameful thing. Tertultian (c. 200) ECF 3.509.
14. Such sins are committed by fornicators, adulterers, abusers of themselves with men, effeminate men, idolaters, and murderers. Origen, Commentary on Matthew 14.10 (c. 245).

In light of these facts, anyone who wants to argue that homosexuality is OK, for Christians today, must begin to prove his statement by finding a first century church father or secular historian that would use the words to mean something other than homosexuality.

The burden of proof is on them.

All references NIV, unless otherwise noted.