Pilates! I'm a very strong advocate for this - combined with cardio - you will really see your body change! i just recently started doing it again (i use the winsor pilates accelerated body sculpting one) and i love it. it makes you flexible and lean and it is the best workout for your abs. everyone must do pilates!
i am not a fan of yoga - the poses are held too long and i don't feel like my body got a proper workout afterwards. pilates a couple times a week will transform your body!