I use three things for lower back health. First, this workout by Dr. Stuart McGill is a mainstay...I've been doing it for years and have had little if any problem with my low back since: http://www.acefitness.org/pdfs/LowBackStabilization.pdf
His publication, Ultimate Back Fitness and Performance, is probably the "bible" when it comes to core strength and back health. I also swear by the stretches he recommends...much safer than the mainstay found on the web.
Also, if you can find the booklet, Robin McKenzie's Treat Your Own Back might/might not be something to use. I've had mixed results with it and don't recommend buying the book but finding the exercises on the web, if you can, so you don't waste your money if the program doesn't work.
Hope that helps.