With cardboard, you can make aesthetic and cheap furniture.

Tutos
A shelf. (License CC BY)
https://www.youtube.com/watch?v=-OMd7NDahOE

A wall shelf. (License CC BY)
https://www.youtube.com/watch?v=dKqa2i0EMUk

A wardrobe. (License CC BY)
https://www.youtube.com/watch?v=Z_U1RUuiNuA

Pictures

Photo : Ambrishraja, Creative commons BY SA

Photo : Gilboonet, Creative commons BY SA
A stage of the construction.

Photo : Gilboonet, Creative commons BY SA
Finishing done.