David, thanks for the tips. There is a large waterfall in the Catlins that I have heard about. I'm not planning on spending too much time along the coast, since that is pretty much like where I live now. I grew up next to the mountains in Colorado, so I was thinking about spending time where I could see them, and still be near a body of water - like Lake Wakatipu, Lake Wanaka, Lake Hawea, perhaps somewhere along the Waimakariri River as well. I'm going to try not to drive too much though, so I don't where I will actually visit. I've actually driven the route from Balclutha to Alexandra (I have a close friend who works for the Central Otago District Council).
I am also planning on spending about a week on the North Island as well; I think that Sean and John McCallum are planning on a get together somewhere around Auckland during that time. If that is too far for you to go, I could come down closer to Wellington during my trip if you would like to get together. I don't have any plans for my time in the North Island yet, other than spending my last day in Auckland.