My Mom recently loaned me her copy of Evangelical Truth, by John Stott. And while there are occasional bits that I would disagree with, there are also some brilliant passages. What follows is Stott's paragraph on justification by faith, perhaps the best thing I've ever read on the subject.
We are "justified by faith." This is the most frequently repeated of the expressions about justification in Paul's letters. It was a sure instinct of Luther's to add the word alone to his translation of the Greek of Romans 3:28, as several early church fathers had done before him. Since our justifcation is altogether "apart from observing the law," it must be by faith alone. In saying so, however, we must be careful not to turn our faith into another work. We are indeed justified by God's grace and by Christ's blood, but only through faith. To say "justification by faith alone" is another way of saying "justification by Christ alone." Faith has no function but to receive what grace freely offers. As the judicious Richard Hooker put it with his usual precision, "God doth justify the believing man, yet not for the worthiness of his belief, but for His worthiness who is believed." Faith is nothing but the hand which takes the gift, the eye which beholds the giver, and the mouth which drinks the water of life.