Wai-O-Tapu Geothermal Wonderland Websitehttp://www.waiotapu.co.nz/
The pictures on the website may inspire you. Especially, check out the pictures of Champagne Pool.
Te Puia Official Websitehttp://www.tepuia.com/index.htm
Te Puia is a Maori cultural centre, but in addition to Maori culture such as weaving and carving, you can enjoy geothermal sites including mud pools, geysers, and steaming vents there. It is a bit touristy, compared with Wai-O-Tapu.
Maori Wood Carving, Te Puia Videohttp://www.youtube.com/watch?v=kvbPk9WJSX0
A carving trainee shows haka (traditional dance) and Maori's greeting in this short film. It is possible to make a quick tour of the carving institute of Te Puia.
I visited Rotorua twice while I was in New Zealand. Rotorua must be one of the best tourist attractions of New Zealand and it's very accessible from Auckland by bus. The streets smells of sulfur all the time and it was the first time to visit a smelly city like that. I walked around all over the city and enjoyed geysers and boiling mud pools. Kuirau Park is located in the centre of the city and it is admission free. I liked strolling around the shore of Rotorua Lake to see some small geysers around the lake and it was also free. That means everyone can enjoy some attractions of Rotorua for free. Tourism Rotorua next to the bus port was very helpful to find attractions around there. The best attraction I tried was WaioO-Tapu; Champagne Pool was truly beautiful and the Lady Knox Geyser was exciting. Te Puia was close to the city and full of geothermal sites and Maori culture. It's also highly recommendable to everyone. Rainbow Springs and Agrodome are not a geothermal site, but beautiful parks and recommendable especially to families with children.