Those of you with forums of your own may be especially interested in this.
"Software that identifies the most informative people in an online community, based on their posting patterns, has been developed by researchers at Cornell University, New York, and Microsoft Research in Washington State"
No doubt sooner or later there will be bots crawling over this forum looking for the answer. These forums span so much information this question is quite difficult to answer I think.
But it would be interesting if you list a sub-forum and say who you think the mover and shaker in that one is.
To kick the ball off, I would say Ed. and Wately in the Forum Lobby with the spanner.