The Premise: We've never run a superhero RPG on the mud (assuming you don't count Nobilis). I don't think I've ever been in a superhero RPG off the mud either. What the hell? I'm thinking we do the thing where the PCs are newly empowered and trying to put together some kind of team and get to the bottom of the new crime problem in town.
The Time and Players: Not scheduled or signed up for yet. Maybe in July or August.
The Rules: Well, Truth & Justice seems like an obvious possibility. Or probably anything else rules-light and flexible would work.
The Characters: This seems like a case where folks should make up their own characters as opposed to me using pregens. With the given premise, characters should be newly empowered and interested in fighting crime (or at least willing to get interested). I'm not quite sure of the power level we're talking here -- I suspect with a team, you're better off going for X-Men level rather than Superman or even Spider-man.