This will be certainly predicated on personal preference, but what movies have you purchased or seen with extra commentary where you felt it was well worth it? I don't download movies in general. If there is a movie I think is important, I'll just buy a DVD or blue ray.
I would also say that there are some movies where you can watch "Making of __" on Youtube that are rewarding. Examples would be Mad Max, Bladerunner and Jaws.
As far as ones I've seen recently, Fast Times at Ridgemont High has excellent commentary through the whole movie by Cameron Crow and Amy Heckerling. I think I bought it in a pack at a gas station with Animal House or Pretty in Pink or something, but the other movie had no useful material. The Fast Times commentary goes through the entire casting process and even discusses the sound track. Apparently it wasn't the soundtrack they wanted, but damn if I don't like it.
I would also say that there are some movies where you can watch "Making of __" on Youtube that are rewarding. Examples would be Mad Max, Bladerunner and Jaws.
As far as ones I've seen recently, Fast Times at Ridgemont High has excellent commentary through the whole movie by Cameron Crow and Amy Heckerling. I think I bought it in a pack at a gas station with Animal House or Pretty in Pink or something, but the other movie had no useful material. The Fast Times commentary goes through the entire casting process and even discusses the sound track. Apparently it wasn't the soundtrack they wanted, but damn if I don't like it.