Many of the stretches and postures used in yoga can help to keep the back supple and strong. There are many excellent videos available if you just don't have time to spare for a class, or can't get coverage to be away for that time. (There really is no substitute for a good yoga teacher and class, but a video is certainly better than not protecting your back at all!!)
The video that I found most useful is one by Rodney Yee, entitled: Yoga for Back Care. It is available on DVD from Gaiam.com at the following link: Yoga for Back Care
There are also several other products you might find helpful. One is created by the Mayo Clinic, also available at Gaiam.com. Mayo Clinic Wellness Solutions for Back Pain
It is crucial to find a method of stress relief and body care that feels good, is right for you, and works -- so that you will be encouraged to keep doing it. For me, that is yoga. Try one of these, or some other yoga video or class, if that's more appealing. Just do something proactive today for your own health, wellness and stress relief.