The Appendices (Lord of the Rings Trilogy)
Probably my #1. So comprehensive and well done. Always interesting.
Rush Hour 1 & 2 - I really enjoyed Brett Ratner's commentary on these movies. I know, it's not a pair of movies you would really think to bother listening to the commentary on (or maybe you wouldn't think to watch these movies at all), but Ratner is a really enthusiastic and fun director to listen to (at least at that point in his career, I have no idea what he's like now). He has an undeniable passion for cinema, and a knack for telling the stories of making the movies. If I remember right it's just him for the entire commentary... it's pretty rare to hear a solo director commentary where the person speaking is so animated and into telling the story. More typically the person sounds bored, or just too relaxed, like they're only speaking to themselves... and it comes out dull. I just remember being very entertained by Ratner's anecdotes about the shoot, and found his passion infectious. It really made root for him in the future because I just found him likable and genuine. Sadly I think Rush Hour 2 was the last film of his I enjoyed.
Nothing else really comes to mind though.