Holiest Of All Andrews Murray's devotional commentary on the Letter to the Hebrews is simply the best.
Word Biblical Commentary, Vol. 47b, Hebrews 9-13 Volume 2 of Dr. Lane's outstanding commentary covering chapters 9-13.
Word Biblical Commentary Vol. 47a, Hebrews 1-8 This outstanding volume covers the first 8 chapters of Hebrews.
Hebrews (The Anchor Yale Bible Commentaries) This is one of the most worthwhile commentaries available on Hebrews.
Be Confident (Hebrews): Live by Faith, Not by Sight (The BE Series Commentary) An ideal commentary for use in your Sunday school class or Bible study group.
Hebrews (Tyndale New Testament Commentaries) This is a thoroughly readable, accessible and affordable introductory commentary to Hebrews.
The Epistle to the Hebrews (The New International Commentary on the New Testament) This is a MUST read for students of Hebrews!