Exercising With a Stability Ball

Have you heard about them? I finally bought one a few weeks ago and I love to work out with it... I bought the dvd/ball combo and have used it a couple of times and just need to get into a routine of using it more often. It is supposed to help trim your middle area and tighten things up a tad :) It is an easy workout, but you will use muscles that you don't normally use. Here is a link to one from eBay http://cgi.ebay.com/The-Firm-Core-STABILITY-BALL-55cm-w-DVD-exercise-NEW_W0QQitemZ260283656633QQihZ016QQcategoryZ31390QQssPageNameZWDVWQQrdZ1QQcmdZViewItem