I used to have terrible back problems before I started working out. Have never used anything specifically for back but here are some things that have really helped in my case (and I would definitely recommend a "holistic" approach rather than just concentrating on the back):
-Strength training, including but not limited to, back and abs (best when you are healthy, of course).
-Attention to posture: some workouts will remind you of good posture (I tend towards swayback and have to remember to tuck those hips under).
-Flexibility: I know that in my case tight hammies will "pull" on my back so I try to do yoga or at least some stretches several times a week.
Good luck--hope you feel better soon!