As racism becomes more popular in our culture, I give it about a decade before "interracial" marriage becomes taboo once again. For now, however, opposition to "interracial" marriage is rightly considered bigoted. This is such a strong contention that even many atheists use the "fact" that the Bible is opposed to "interracial" marriage as evidence that it is just the outdated opinion of bronze age goat herders.
But contrary to their assertions, the Bible never actually opposes "interracial" marriage. This is a slanderous claim, made only by heretics who abuse the Bible in many ways, or atheists who seek to oppose it. You can read the Bible as often as you want, forwards, backwards, or upside down, such a command is never found within its Holy pages.
Of course, properly defined, the Bible is against interracial marriage. A man cannot marry a monkey. But although atheistic religions, such as Evolution, teach that there are multiple human races, that the Caucasian is the highest of these 5 races, that it is ignorant to allow the other 4 to breed, or that the other 4 are savage and will no doubt later on be wiped out, the Bible contains no such vile vociferations against those who are made in God's image.
Biblically speaking, there is one race. You can be "white", you can be "black", you could even display some skin tone that has never been observed before, you are the same race as any other human being. Thus, Biblically speaking, a marriage between one man and one woman is usually legitimate, though of course there are exceptions.
Skin tone is not one of them. In fact, this issue is addressed quite clearly in the book of Numbers. Specifically in Numbers 12, Moses, by far the most prominent prophet apart from the Good Lord Himself, finds himself at odds with Aaron and Miriam, who are very unhappy about the fact his wife is Ethiopian. So God calls the three to the Tabernacle of Meeting, gives Aaron and Miriam a stern rebuke, and Miriam is struck with leprosy. Moses attempts to intercede for her, and she goes through the standard purity procedure until she is clean.
To any sensible human being, the marriage of one of God's most prominent prophets to a woman from one of Israel's most notorious enemies is enough to show that "interracial" marriage is not a problem. Of course, the kind of skeptics who would claim it is are rarely sensible. Nevertheless, the fact is, Biblically speaking, there are no racial reasons one person should not marry another.
But one kind of marriage that is never considered wise is the marriage of a believer to an unbeliever. "Do not be unequally yoked together with unbelievers. For what fellowship has righteousness with lawlessness? And what communion has light with darkness?" (2 Corinthians 6:14). The concern here is not one's national origins, but temptation. Spiritually, a legitimate marriage between a believer and unbeliever is still considered clean, and Scripture even commands believers who are married to unbelievers to stay married, if indeed the unbeliever is content to stay. But marriage, being a partnership, will inevitably result in one partner pulling the other in a different direction. The ideal, of course, is that the Christian will lead the unbeliever to Christ. But there is also a very real danger that the unbeliever will hinder the faith of the believer.
Ultimately, marriage is designed as a reflection of Christ's relationship with the Church, not as some mark of superiority. It is a truly beautiful thing, designed even before the fall of man, but also foreshadowing a far greater relationship. When we depart from our spouse in this life, we become united with Christ in the next, a far greater relationship that will last for all eternity. This was achieved by Christ's own death, for as a good husband will lay down his very life for his wife, Christ died on the cross to absolve us of all our sins. This reward can be received as easily as an engagement ring: He offers it to us, and we accept by confessing Him as Lord, and believing God raised Him from the dead.