I've recently found a couple of things that help:
1. A book called "Pain Free at Your PC" http://www.amazon.com/Pain-Free-at-Your-PC/dp/0553380524
It has special stretches, some yoga inspired, to counteract the problems developed from sitting for long-periods.
2. A got a think called a "butt-cushion". I was skeptical when my friend suggested it, but felt some relief almost immediately.
Hope these ideas help someone.