I am a big fan of "making-of" videos. I always watch these videos from SoundWorks Collection. They describe the whole process of designing the sound for a variety of movies. The latest one is for Avengers: Age of Ultron.
There is so much action in this movie. It is incredible to hear about how they layered and created all of the sound effects. I especially like the portion of this video that talks about creating the sound of Ultron.
SoundWorks Collection also did the sound for Godzilla, Interstellar, Man of Steel and Gravity. I always think it is a lot of fun to read about and watch how movies are made and the collaborative effort that goes into the final product.