Those who fall into the Huhne / Redwood category are John Hutton and John Denham. Whether either of them want to risk the consequences, which would not be pretty, of running against Brown seems extremely unlikely. But if either of them really does want the top job, now is their moment to move.
One other scenario to keep your eye on is the stalking horse that wounds but doesn’t kill. Imagine if a candidate announced saying, ‘I just want the party to have a choice so a vote for me is a vote for a leadership contest’ and got significant support. At this point, the floodgates would open and Alan Johnson or Jack Straw, the wiliest operator around, could emerge as a caretaker leader.