could be a ball joint, strut, tie rod or control arm bushing. If its a cv joint you can get it replaced for less then what the other people are saying.the part is about 75-150 depending on wether the joint is completely damaged to it just needing relubbed and a new boot on it.
I have the same car and it's not the cv axles. I think it's something in the steering shaft or rack and pinion. Mine has been doing it since I bought it at 30,000 miles it now has 130,000 and nothing has broken or failed because of this. It is a common problem in this car I believe there is a Technical Service Bulletin from GM saying it's the universal joint in the steering shaft.