Exciting news! The IGDA has formed a special-interest group on alternate reality gaming. So far we've got a main blog and a mailing list, with plans to grow as needed.
We're aspiring for this group to be a place for puppetmasters to share information and strategies with each other, with an eye toward making stronger and more successful games for everyone. If you're an ARG developer, or if you have something you'd like to bring to the discussion, we'd love to have you join!