If you're anything like me, variety matters. In my workout DVD collection, I aim for a range of workout lengths (anywhere from 10 minutes to one hour) and intensity (from gentle to challenging).
Karen Voight's "Slim Toning on a Ball" fits nicely in the middle of both the length and the intensity ranges. It runs half an hour in length, and is on the easy-moderate end of the spectrum with a few challenging spots. You'll need a stability ball and some hand weights (ideally a light set and a heavy set). Karen is friendly and encouraging, but not effusive or annoying.
Reviews here, here, and here.