What about the Brazilian engineering firm Semco? Follows a non-hierarchical, self-organizing structure. Thousands of employees, very successful. Described in two books by CEO Ricardo Semler: The Seven-Day Weekend and Maverick. http://www.amazon.com/The-Seven-Day-Weekend-Changing-Works/d...
Books by the SEMCO founder, Ricardo Semler:
Maverick - http://www.amazon.com/Maverick-Success-Behind-Unusual-Workpl...
The Seven Day Weekend - http://www.amazon.com/Seven-Day-Weekend-Changing-Work-Works-...
There are many companies that operate using democracy as an organizing principle - Semco is the great-granddaddy of them all (two books - Maverick[1] and the 7 Day Weekend[2] - were written by Semco's founder, Ricardo Semler, about how Semco operates).
Other well-known democratically-run companies include Zappos, WL Gore, DaVita (a $12B company), and Dreamhost.
If you're interested, take a look at WorldBlu[3] for more - they've been building a community of these kinds of companies, have tons of resources on their site, and even have a conference on organizational democracy.
[1] - http://www.amazon.com/The-Seven-Day-Weekend-Changing-Works/d...
[2] - http://www.amazon.com/books/dp/0446670553
[3] - http://worldblu.com/
http://www.amazon.com/Seven-Day-Weekend-Changing-Work-Works/...