There are now 13 undefeated teams in FBS. Of these 13, 6 have played (and beaten, of course) teams with only 1 loss.
Oregon, Auburn, LSU and Nebraska have each beaten one team with only one loss.
Two teams have beaten two teams (each) with one loss: Oklahoma, Michigan State.
So, right now, OK and MSU should be #1 and 2 and heading for the BCS Championship game. (of course, MSUs two one loss-team victories are underdogs this week)