Tom Malone, founder of the Center for Collective Intelligence at MIT Sloan discusses his group’s efforts to find out what gives groups superior cognitive abilities across a wide variety of tasks. Statistically, group intelligence only moderately correlates with individual intelligence;the most important attributes proves to be social perception, taking turns in discussions, and percentage of women in the group.

See also -

• Climate CoLab —applying the principles of collective intelligence to solutions for global warming. 
• Irving Wladawsky-Berger’s blog
• Handbook of Collective Intelligence,  a survey of the field of collective intelligence, summarizing what is known, providing references to sources for further information, and suggesting possibilities for future research.
• Blog by Andrew Revkin in New York Times, Exploring humanity’s evolving ‘global brain’