SES moderator Detlev Johnson has resurrected the twice-weekely moderated discussion list that was once one of the few sources of regular interaction for the search marketing community back in the early days. The long-lost I-Search discussion list, originaly moderated by Marshall Simmonds, predated most search forums, and was a regular hangout for most of us back then.
Detlev's new mailing list is named, appropriately enough, SearchReturn, and it has all the familiar trappings of I-Search. One of the nicest aspects of the list is that it's carefully moderated by Detlev, so you only get on-topic, thoughtful posts in the twice-weekly mailings.
Andrew Goodman, the last editor of I-Search before it died, created his own discussion list that's also worth checking out. SEM 2.0 is an invitation-only Google group, and members are expected to have intermediate to advanced search marketing experience to join.