Yes, so if you were in Bible class in Millersburg on Wednesday, and you can think back to before the baptism (which I'll completely forgive, because really, baptisms rock and all), I mentioned that I disagreed with the teacher of the class concerning the phrase "only in the Lord" at the end of 1 Corinthians 7.
Now before I launch into what's sure to be a very short defense, as the post below points out, I'm feeling lazy tonight, let me first say that its generally inadvisable to publicly state that you are disagreeing with an elder of the congregation. Thankfully, John is rather feisty and can hold up to an argument such as this, as most elders can.
My thoughts are that the phrase "only in the Lord" are referring to the manner in which the widow is to remarry rather than the actual person that she is to remarry. Earlier in the chapter, Paul points out that it is not a sin to be married to someone outside of the body of Christ. It is a situation in which many men and women find themselves today, coming to Christ already in the marriage. In the first century, the situation was different than we have in the United States today, for if someone would become a Christian in those days, especially a woman, she ran the very large risk of her husband being perturbed by her joining herself to people whom he did not like or associate with and would leave her. For this cause, Paul says that she is not bound to him to leave the Church to retain the marriage.
But if it is the case that he would remain, or that she was married to a Christian in the first place, and her husband would die, God does have some directives for her. She needs to realize her responsibility to God rather than to her own sexual desires. In 1 Timothy 5:11-12, the church is warned to not take young widows into their benevolent programs (ugh, I hate that terminology, but can't think of any better), because there was a very clear risk of them wandering from the faith because of their sensual desires. It is a risk that has been around for thousands of years, that we still struggle with in the twenty-first century. It is in this way that we can take in Paul's idea here in 1 Corinthians. When the widow chooses to marry, her first thought should be to keep God at the forefront of her decision making. The phrase would be closely associated with another that Paul makes, "Children, obey your parents in the Lord, for this is right..." (Ephesians 6:1). Paul is not directing children to only obey Christian parents. He is telling them that they are to follow the teachings of their parents that are true and good, and as they do so they are following what the Lord wants them to do. He doesn't want them to be rebellious, and he doesn't want the widow's search for a husband to be a rebellion against God, thus, "only in the Lord".