My thought for the day on this issue comes from 1 Corinthians 13, where Paul speaks of charity. Note particularly verses 2 and 13:
2 And though I have the gift of prophecy, and understand all mysteries, and all knowledge; and though I have all faith, so that I could remove mountains, and have not charity, I am nothing.If faith alone really were sufficient for salvation, I would ask how one could have all faith - real faith that can move mountains - and still be nothing if charity is lacking? I would also ask why charity would be said to be the greater than faith? Wouldn't it be safer to say salvation is by charity alone, or at least by charity plus faith alone? But then the faith isn't very alone anymore.
13 And now abideth faith, hope, charity, these three; but the greatest of these is charity.
There are passages in the New Testament where Christ is asked what one must do to gain eternal life. His responses never came close to teaching "faith alone." Rather, he spoke of following God through obedience to commandments and through taking care of others (charity).
By the way, for an interesting Protestant discussion of the meaning of James 2:14, "faith without works is dead," see "Can Faith Without Works Save?" by Bob Wilkin at FaithAlone.org. I find much of his discussion to be persuasive and helpful in understanding that oft-maligned verse, James 2:14. But their statement on how one achieves salvation is something that strikes me as rather incomplete in light of the teachings of Christ in the Bible. But that's just my LDS-oriented opinion, of course. The fact that I disagree doesn't mean I think my fellow Christians who share that view should be condemned as cultists or non-Christians.