I needed an exercise that would get me moving, and yet be gentle on my joints. Believe it or not, hula hooping is a great exercise! Gets me moving, is great for the lower back, and it has given me curves I never thought I would have.
The Walmart variety do not work, even as a kid I could not make them go. Some upscale health clubs are starting to advertize them, but I made my own. Go to a hardware store and get 12 or 13 foot of 3/4 or 1 inch black underground sprinkler hose, and a connector. Hook the ends together, and voila! To make the hoop slip proof, I wrapped some cloth tape around it.
It does take a bit of practice to make it fly, but that is the fun! It is so goofy, that one can't help but smile while learning. Music makes it fun, too. Just be careful the first week. You will have sore obliques, and paunch. After a few weeks or so, you will see a change! Also, your back will be more flexible.
Here is a good intro site that talks bout hooping - http://hooping.org