Audio commentaries on DVD or Blu-ray sometimes provide a great insight into the filmmamking process. What are the best ones?

Ridley Scott on "The Duellists" is petty good at talking about the film making aspects of the film.

There are something like 16 hours of special features and such on the extended edition of the Lord of the Rings DVD box set. I found them fascinating, both for the scale of the work and especially the art direction and realization. And then there are the amazing models...

The commentary for "Paper Moon" is very interesting. They talked a lot about the lighting they had to do for all the deep focus shots.