Sun salutations are a great way to relieve lower back pain. At the bottom of this post is a diagram of the sun salutations, and if you click on it it will lead to you to a site with detailed instructions on how to do each move properly.

One thing to be careful of is that there are a couple of moves in the standard sun salutations that are not really good for your back, so I suggest you modify them. These are the ones that involve bending your back while keeping your knees straight. That is not very good as it places undue pressure on your sacroiliac joint. Instead just bend your knees for these moves (and if you want to loosen your hamstrings, go do a different stretch).

Sun salutations are really good to alleviate back pain as they stretch your spine. So if you just give 10 minutes each morning to doing these, you will get stronger and looser muscles, and less pain.