I do a ton of ab work on the stability (swiss) ball. Here are a couple addresses to visit for ideas of what to do:
http://www.acefitness.org/fitfacts/f...cfm?itemid=126
www.onlinefit.com/health/index.cfm/Category/90.
Also, I got a book out of the library that had like 53 exercises to do on the ball, not just ab work. I'm sorry I can't remember its name, but you might try searching Amazon or something.
hope this helps!
lynne