gym balls!!

Are you talking about a weighted medicine ball? I use mine for wall ball squats, lunges w/ a twist, and russian twists for abs. I think they are a good addition to a workout but I've yet to build an entire workout around them.

Last year I have been doing pilates with the swiss ball and it greatly improves balance and it is also fun. But It is important do do it properly or you can injure yourself. I think that it will be better for you to do one month with a trainer to learn the exercises and then do it by yourself.

Stability balls, Gym balls, Swiss Balls..... a rose by any other name!

There are some pretty hard core exercises you can do on these things. If you have one of the toughened anti-burst ones, you can use it as a kind of weight bench: adds a layer of instability and core activation. There are a metric tonne of core/arm/leg exercises you can incorporate with one of these. There are plenty of books out there, some videos, probably a lot of youtube type resources. You could put together a routine that was a hundred times harder than anything in 30DS.

Form is absolutely king with these things though.... if you don't engage your core properly you will a) not get the benefits from the exercises and b) possibly injure yourself! If you have good body awareness and core engagement then use some online resources and have at it. Or else a short class might be in order to show you the basics.....