Handily enough, this month's Men's Journal has a special article about the back in it. I recommend buying it anyway since it's got Gerard Butler on the cover and a lovely interview with him, but here's the back exercises they recommend (now that I've got a minute to write them down!).
These would be exercises to do once your back is better, to strengthen it. I haven't actually tried them myself yet - only just finished reading the interview with Gerard
1. Bird Dog: Kneeling on all fours, with your back flat, extend your right leg backwards, then your left hand forward. Hold for five seconds. Repeat 15 times, then switch sides.
2. Hip Flexor Stretch: Kneeling, place one foot flat on the floor in front of you. Lunge forward and raise your arm straight up on the opposite side. Hold the stretch for 60 seconds five times on each side.
3. Single-leg Bridge: Lying with your arms at yours ides, extend one leg straight out and raise your hops off the floor. Hold for two seconds; repeat 15 times on each side.
4. Downward Dog: From a V-shaped position (going by the photo - making a V with your legs as one side and your arms and back as the other, so with your hands and feet on the floor) lift your heels as you shift your weight to the balls of your feet; hold for three seconds. Lower your heels, pointing your toes upward; hold for three seconds. Repeat 10 times.
These would be exercises to do once your back is better, to strengthen it. I haven't actually tried them myself yet - only just finished reading the interview with Gerard

1. Bird Dog: Kneeling on all fours, with your back flat, extend your right leg backwards, then your left hand forward. Hold for five seconds. Repeat 15 times, then switch sides.
2. Hip Flexor Stretch: Kneeling, place one foot flat on the floor in front of you. Lunge forward and raise your arm straight up on the opposite side. Hold the stretch for 60 seconds five times on each side.
3. Single-leg Bridge: Lying with your arms at yours ides, extend one leg straight out and raise your hops off the floor. Hold for two seconds; repeat 15 times on each side.
4. Downward Dog: From a V-shaped position (going by the photo - making a V with your legs as one side and your arms and back as the other, so with your hands and feet on the floor) lift your heels as you shift your weight to the balls of your feet; hold for three seconds. Lower your heels, pointing your toes upward; hold for three seconds. Repeat 10 times.