Really, it depends on what shot I want to play. If I want to get the ball up in the air, I play closer to my front, but for most chipping, the ball is off my back foot.
Well there are a number of shots around the green where you will be using your wedges. However if a straightforeward chip shot I will have the ball forward in my stance, with my weight on my front foot, the club face open, and accilerating through the shot. I have found that chipping this way gives me more soft landings on the green. Especially helpful for those mid length chips where you have to get it over a bunker or some sort of hazard and then land it softly on the green.