I have rewritten this post with some updates. Since returning from the regional conference this weekend there has been some considerable discussion on Hebrews in the blogosphere:
Better Bibles Blog has a couple of posts on Hebrews 1:3 and what the phrase "word of his power" means. See The Word of His Power and His Powerful Word. Be sure to read the considerable discussion. In response Bob MacDonald offers his own translation of Hebrews 1:1-4 on his post My insufficiency.
Michael Bird has a post on Hebrews 5:11-6:12 in Perseverance in Hebrews on Euangelion. James Gregory has posted a response on his eponymous blog, along with links to his earlier reflections on the passage. He includes a link to Ben Witherington's post on Christian Apostasy and Hebrews 6 from last year. I think that the passage is a real warning about the danger of apostasy. Otherwise, why would the author of Hebrews have bothered to say anything, if it wasn't a real possibility?
Tony Siew on his blog Revelation is Real has a post on Faith in Hebrews.