Which theories do you know about the information society (from which
authors, maybe you can also give a brief summary) and which one would
you preferably discuss in an article about the UN world summit on
information society.

I am not a google researcher.  However, I thought you might find Peter
F. Drucker's article , "The Age of Social Transformation", The
Atlantic Magazine, Nov. 1994, Vol.275, iss. 5, Page 53 (18 pages) an
interesting read. He speaks about the knowledge(information) society
in depth. Go to the www.theatlantic.com and search in the archives for
the article. You will have to purchase the article. The magazine
offers up this abstractre the article:

"Although the 20th century will be remembered for its horrors, its
most profound legacies are radical transformations of work and
society. The need for public perception and institutions to respond to
the transformations is discussed"