I don't know if anyone posted this before, but I was skimming through Video Google the other day and came across this: http://video.google.com/videoplay?docid=-7791992304107970746&q=Half+Life&hl=en
It's a very well-done (IMHO) commentary of HL2:EP1 by a fan of the game. My brain's been completely blank for the last week so feel free to add in your own comments.