William Varner talks about his experience of seeing the oldest extant manuscript of the book of Hebrews, P46, in the Chester Beatty Papyrus collection. He notes that even in this oldest of manuscripts the title was "To the Hebrews." He gives a picture of it here.
Steven Coxhead has a discussion on The Eternal Nature of the Eternal Covenant in Hebrews. He has a follow-up discussion on When Jesus Became Our Great High Priest after the Order of Melchizedek.
Zondervan has posted an excerpt of the complete chapter on Hebrews from Carson, Moo, and Naselli, Introducing the New Testament.
Arminian Today has a meditation on Hebrews 7:23-28 entitled, Jesus, My Faithful, Perfect High Priest.