- yoga (which you've got covered)
- a kneeling chair does wonders for posture
- placing your monitor at the proper height (eye-level is 1/2-1/3 from the top of the screen otherwise you tend to crane your head forward and downward)
- stepping away from the screens regularly (set a timer to remind you because it's easy to blow this one off)
- eye exercises (especially this one...alternate focusing on the tip of your nose and focusing on a far distance)
Good luck
Ubuntu includes an application to enforce breaks by locking your screen. I have tried it. Works.
Buy one of these (way too expensive) keyboards:
http://www.kinesis-ergo.com/images/freestyle-solo_690x375.jp...
Then build one of these out of a cardboard box and duct tape:
http://www.kinesis-ergo.com/images/solo-ascent-90_512x390.jp...
For the vertical layout, the spacing of the keyboard prevents wrist bending: the two sides of the keyboard are roughly shoulder width apart. When you aren't typing, the natural thing to do is put your hands in your lap.
Yoga has been helpful, but I'm wondering how long I'll be able to cope.