Now that Clark is closer to being Superman than being a mere meteor freak in Smallville, he’s starting to interact with the DCU at large. Sure, there was the “Junior Lifeguards Association” a few years ago, and Green Arrow is a regular character, but Smallville was pretty insular. Then last season happened, when Geoff Johns was tapped to pen the episode “Legion.” And this Friday, Well, he’s back, and now he’s writing “Society.”
and now we know who they are:
He has been sketchy on who was going to be in the episode, but now we have confirmation that Hawkman and Dr. Fate are going to be played by Michael Shanks (Stargate SG-1, Burn Notice) and Brent Stait (Gene Roddenberry’s Andromeda, Stargate Atlantis), respectively. And we also have a third member, Star Girl, all but confirmed.

Brent Stait will be Dr. Fate.
UPDATE:
Stargirl has been confirmed, and will be played by Britt Irvin from Hot Rod and Aliens in America. All three of these seem to be great choices for the roles of the JSA members.
Britt Irvin
Society is airing in January.