POWERx the stability ball can I highly recommend. Had a double herniated disc three years ago. This of course always backache. Since I use this ball in the office, I hop on that sitting around, doing pelvic exercises and sit upright and straight. Back pain have since become massively less. People, what do for your back and sit on those balls. Initially, it is inconvenient and painful, but after a week it's all gone!
