Seven Consensus Methods ( Development Years 1972-2011):

(1) Nominal Group Technique,

(2) Interpretive Structural Modeling,
(3) DELPHI,
(4) Options Field,
(5) Options Profile,
(6) Trade-off Analysis, and
(7) Webscope
For an elaboration of six of the seven Consensus Methods see How People Harness their Collective Wisdom and Power:

http://www.amazon.com/gp/product/1593114818/ref=ed_oe_p/104-7420823-4256710?%5Fencoding=UTF8

For a more thorough discussion of the Consensus Methods the interested reader should consult:

Warfield, John N., and A. Roxana Cardenas. A Handbook of Interactive Management. Ames, Iowa: Iowa State University Press, 2d, 1994