In nuno-felting, wool and textile are felted together to form a new fabric. Textiles such as silk, cotton, silk gauze, wool, hemp or linen can be used; here discarded silk saris and other recycled clothes of silk or cotton are mainly used.
A couple of pictures of the process:
For a short description of the process, see here. There are many explanations of nuno-felting available online. For an account of my methods, see my book Old Clothes in Disguise.
Two other books that I can recommend are:
Inge Bauer: An-Gewand-t felted. A Gallery Book/Felting Impressions, MaroVerlag, Augsburg (2010).
Lizzie Houghton: Felting Fashion, Creative and Inspirational Techniques for feltmakers, Batsford, London (2009).
Henriette Giese