I would like to recommend a great Auckland tour operator called Potiki Adventures which created an unforgettable day for me. The trip I booked was called Urban Maori Experience and took me to urban sightseeing places and urban bush sites.
The special thing about them is that they give insight into contemporary Maori culture, telling and showing the way it is practiced today. It felt really authentic, much more than what tourists can experience at the (commercial) Maori shows in Rotorua!!!
To me, it felt like I was spending a day with friends. Melissa (the guide) was just so lovely and enthusiastic! They are just great!!! This is for everyone who looks for a unique and authentic way to experience New Zealand.
Potiki-Adventures have also a homepage: www.potikiadventures.com. I think they offer a Marine Reserve trip in the summer and they have some customized tours.