For ZBrush? go to www.pixologic.com
It is a modeling /3d program that will cost you about 500$, but the free demo you can download to see all of the great features in it. The main thing is that you can paint directly on a surface, no UV's involved. In a way, as you paint it maps the UV's all on its own. Its amazing. I just downloaded the learning edition, and, unlike Maya PLE it has no watermark!