I do squats with varying regularity.
I usually take 2 workouts from the core advantage book, and when I get to the squats workout I change it up and do 5 push-up sets of about 7 push-ups. After each set I do a set of 15 squats for 4 sets.
This has really helped me stay loose and avoid back pain.
I wish I did these twice a week, but I get lazy and sometimes miss a week. When I do I feel my body starting to tighten up and back pain return.
I off set the push-ups at the end of the workout with a couple of sets of curls and 2 sets of 5 pullups. Without off setting the push-ups I find I run into a lot of upper back issues.