i posted about this a long while ago on another forum:
http://www.bodybridge.com/i can't seem to figure out how to post a pic with this mac i'm on, but regardless, this little doohickey is pretty cool. it's a cushioned arch you lie on that lets your back slowly stretch.
i tried it and like it much more than inversion machines, which seemed to pull my knees. also like it over those giant body ball things, which i think pose some safety hazards for the less equilibrium minded amongst us.
bodybridge looks slightly torturous, but feels great.
i love a good back stretch!