As I am preaching through 1 John I thought I would share some of the resources that I have found to be very helpful in understanding this New Testament letter.
Beeke, Joel. The Epistles of John. Webster, NY: Evangelical Press, 2006. beginner, layman friendly, very pastoral
Boice, James Montgomery. The Epistles of John: An Expositional Commentary. Grand Rapids, MI: Baker, 1979. beginner, layman friendly, very pastoral
Calvin, John. Calvin’s New Testament Commentaries. Vol. 5, The Gospel According to St. John, Part Two, and the First Epistle of John. Reprint, Grand Rapids: Eerdmans, 1961. intermediate, pastor-scholar
Carson, D. A. and Douglas J. Moo. An Introduction to the New Testament. 2nd Ed. Grand Rapids: Zondervan, 2005. intermediate, pastor-scholar
Kostenberger, Andreas J. A Theology of John’s Gospel and Letters. Biblical Theology of the New Testament. Grand Rapids, MI: Zondervan, 2009. advanced, pastor-scholar
Kruse, Colin G. The Letters of John. Pillar New Testament Commentary. Grand Rapids, MI: Eerdmans, 2000. intermediate, pastor-scholar
Marshall, I. Howard. The Epistles of John. The New Testament Commentary on the New Testament. Grand Rapids, MI: Eerdmans, 1978. intermediate, pastor-scholar
Riddlebarger, Kim. “Sermons on the Epistles of John.” Available at http://kimriddlebarger.squarespace.com/ (accessed 3/9/10). sermons, better be pastoral!
Smalley, Stephen S. 1, 2, 3 John. Word Biblical Commentary. Waco, TX: Word, 1984. advanced, pastor-scholar
Stott, John R.W. The Letters of John. Tyndale New Testament Commentary. Grand Rapids, MI: Eerdmans, 1988. intermediate, pastor-scholar
Yarbrough, Robert W. 1-3 John. Baker Exegetical Commentary on the New Testament. Grand Rapids, MI: Baker Academic, 2008. advanced, pastor-scholar
If I could only recommend one commentary, I would definitely recommend John Stott’s commentary as the best overall. It has the technical aspects of a scholarly commentary but it is very easy to read and often reads like a sermon. It is very quotable.