This was made popular with the movie The Haunting, which was one of my favorite ghost movies. Anyway, this popular effect can be best accomplished by building the door out of a piece of foam rubber 1-2 inches thick and the size of your doorjamb. You will need to build a thin wooden frame the size of the door, and glue the sides of the foam rubber piece to the inside of the frame. This enables it to stay in place as you push against the door.
Next cut strips of thinner foam to layer onto the door, to give it depth around those recessed panels as in the illustration. The foam will need to be glued with a special glue similar to a rubber cement. It needs to get tacky on each side of whatever you are gluing, before you press them together.
The next step is to either cover the door in wood grain contact paper, or have the foam painted. Since painting it can be a pain in the rear, I would recommend the contact paper, although the contact paper might be hard to keep on with the expanding door surface. You could have an airbrush artist experiment with several paints and colors.
Next you will need something to represent the doorknob plate. Some sort of lightweight material like wooden panelling can be used. A lightweight doorknob will also be needed.
After the door is secured in the doorjamb, it will need to be lighted carefully so the guests will be able to see the breathing effect, as the assistant behind the door pushes outward.
The above "How-To" is an excerpt from Tim Harkleroad's "The Complete Haunted House Book" for more information about this and other great haunted house reference books go to MoonLighting Publication's website "Haunted House Books On-Line" at www.hauntedhousebooks.com. You can e-mail Tim at moonpub@aol.com