my pt suggested core exercises as being key to good posture...I am finding that in a well equippend gym that there are things I can do on very specific machines for abs, back, and obliques...but it was a lot of trial and error. The machine has to really isolate the muscle and not reguire me to tense up the neck and shoulders. I can push with my back or my legs, though.

For Abs i also do foam roller exercises...lay on it with your arms crossed over chest, activate abs, lift one leg at a time and use core muscles to keep you balanced on the roll. I can't do anything where I have to lift my head and support it with my neck...hurts way too much.

I do one legged bridges for gluts

For shoulders, I do the kind of pushups where you lay on your side propped up on one elbow/arm (whole forearm on the ground) and use your arm/shoulder to push your body up. Legs stay on the ground. It is a very small movement and I only do a few (started with 5, now I do 10) at a time per side. Trap and neck spasms can make it hard to sink onto my shoulder.
If this description isn't clear, it is sort of like a shoulder shrug... sink down into a shrug, push up out of it, but on your side.

I can't do treadmill...and I have to do bikes/glider/elliptical/stiarmaster on low speed with high resistance because the bouncing bothers my neck.

Interestign to hear what everybody does. Hope to hear more form the rest of you