I think good mornings should be good for posture. If your looking for posture in lifts, what you could do is stand with you back flat against the wall and do your exercise. You could also use a belt. I personally dont use one, but whatever.
Losta stretching in the hamstring and calf area.
(it helps with the pull of my pelvis)
`farmers walks (walking with heavy as you can with dumbells)
`shrugs
`weighted sit ups from a decline (approx 15%)
`abdominal holds (usually it when im on the computer/sitting down)
`external rotations and other rotator cuff exercises
im in the process of building up my whole sholder girdle by doing standing overhead presses.
i guess it depends what your posture problem is.....if its muscle balance related or just plain lazy.