Gene Green gives some brief recommendations on commentaries on Hebrews (as well as other NT books).
James McGrath has some ramblings about "He Learned Obedience" in Hebrews 4. He also has some musings on Christ's Elementary Word in Hebrews 6.
Matthew Montonini draws attention to a George B. Caird Video Clip which briefly shows Caird lecturing on the book of Hebrews. Caird was originally slated to write the replacement volume on Hebrews for the ICC series, but he died before completing it. Since then, the volume has been assigned to Philip and Loveday Alexander. The first volume is expected to come out this fall.