I met the posture-challenge today with mixed success. I did well when I was thinking about it, but whenever I stopped thinking about it I reverted to my old, slouchy ways.
I exchanged my rolly desk chair for one of the straight-backed guest chairs; that seemed to help a bit. Didn't fix the problem though. I still caught myself slouching over in it far too often.
Ah well. Tomorrow I will wage another battle in this war against slouchiness.