RalphJohnson maintains several mailing lists related to patterns. Some have a readership in the thousands.

http://st-www.cs.uiuc.edu/users/patterns/Lists.html 
mirrored at
http://hillside.net/patterns/mailing.htm

See also PatternsDiscussionFaq

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WardCunningham announced the creation of this wiki in an InvitationToThePatternsList.  Ward also posted TipsForWritingPatternLanguages to the patterns list in 1994.