The parts of The Flash, the Green Lantern and Talia Al Ghul (daughter of Ra’s Al Ghul from Batman Begins). The full cast is expected to be revealed over the coming week.
According to both Ain’t It Cool News and IESB.net, Adam Brody (Wally West/The Flash), Common (the Green Lantern) and Teresa Palmer (Talia Al Ghul). Scott Porter, who IESB.net reports was in competition for the role of the Flash, which went to Brody, may have won the role of Superman.
Additionally, AICN notes that “Michael Gough might be appearing as Alfred.” Gough played Alfred in the Tim Burton through Joel Schumacher series of Batman films.