Is that the one that's got sand in it? If so, I used one at a convention a couple of years ago and it can be used a lot differently from a regular un-filled ball. The shifting weight of the sand inside it lets you do upper body and standing stability work. I thought it was a lot of fun and quite a workout.
When you set it on the floor, it just has that extra measure of stability that keeps it from rolling around when you don't want it to, but basically any exercises you do just sitting on a stationary ball are unchanged.
I suppose you could just use a funnel to put 5# of sand in a regular ball, but it would probably be pretty hard to get out of there if it turned out you didn't like it.
Speed comes from what you put behind you. - Judi Ketteler