David Allen, Dean of the School of Theology and Professor of Preaching at Southwestern Baptist Theological Seminary, has a ten-part series on Interpreting and Preaching Hebrews 6.1–8. He is an advocate for the "Loss of Rewards" view of this passage.
I had previously noted that Trinity Evangelical Divinity School posted a four-part video lecture series on Hebrews by D. A. Carson. Transcripts of the four lectures are also available on the same page.
Logos Bible Software is offering for the month of January a free download of Frederic William Farrar's Hebrews Commentary in the Cambridge Greek Testament for Schools and Colleges series.