I do yoga to alleviate soreness. For lower back pain, backbends are particularly useful. Just be mindful of your limits, and always warm up and loosen your muscles by going through a few cat/cows and forward folds.

Here are a few backbends:
Yoga Journal - Poses: Backbend Poses

For beginners, I would recommend cow, upward-facing dog, bridge, camel, and lord of the dance.