The Ponoko blog has a good roundup of incredible cardboard furniture, much of it from a collective of cardboard furniture makers in France known as Les Cartonnistes.
Some of the work of Les Cartonnistes is quite extraordinary, one would never recognize it as cardboard.
I wish I had known about this when I did my slideshow Pulp Furniture: Paper and Cardboard Seating
More cardboard furniture and offices:
Offices Built out of Cardboard for Nothing
Cardboard Office by Paul Coudamy
TreeHugger Picks: Cardboard Recycled Furniture & More
Green Furniture Cut from Cardboard: Collection at CNET