Yep, getting a strong back (from pull type movements, as well as squats and deadlifts) has improved my posture more than anything else. Another to look into is weak/mis-firing glutes (from sitting all the time). Apparently planks (of a certain kind where you squeeze your glutes as well) help for that.

http://www.romphysicaltherapy.ie/best-exercises-to-strengthe...