Are there any tours in New Zealand based on places where the Lord of the Rings films were made?
If you're willing to visit filming locations on your own, the LOTR Location Guidebook is nice.
Often, local tour operators will cover the filming locations nearby or even offer specific half-day or day tours to more remote/harder to reach places. If there's anything LOTR-related to see in the area, there will always be someone more than willing to show it to you.
If you're into hiking (or tramping as we call it down here) I can heartily recommend getting off the road and into our backcountry. You'll be rewarded with majestic scenery while taking in Lord of the Rings locations at the same time. The country has a series of premier "great walks" which are detailed on the Department of Conservation website.
For example, the Tongariro Crossing is widely considered to be New Zealand's best one day walk and will take you through Mordor, crossing between Mt Tongariro and Mt Ngauruhoe (Mt Doom).
The Routeburn track isn't a LOTR location but walking it certainly feels like you're in the movie and the Dart River Valley before the track starts was the scene for Isengard. The track crosses the Southern Alps and I found it absolutely breathtaking.
While these walks aren't tours there are companies that take guided walks although there's nothing stopping you from doing it on your own. Just be well prepared as our weather (particularly in Alpine areas) can change and become dangerous very quickly.
Also, a great resource is Tourism New Zealand's website. If you search that site for "Lord of the Rings" you'll find quite a few tour operators that visit film locations.
There are a few actually, but the most well known is Lord of the Rings Tours, aptly named. While Hobbiton is cool to see the shire area, the locations in the South Island are by far the more spectacular, especially in the area around Queenstown.
This new CnnGo article goes indepth into the new tours and options available to the Lord of the Rings traveller in New Zealand.
From visiting Hobbiton (Matamata), Mordor (Tongariro National Park), Rivendell (Wellywood), The Misty Mountains (The Remarkables) and more, they also include the following links and contacts:
Embassy Theatre, 10 Kent Terrace, Wellington, +64 4 384 7657
Flat Earth, (tours of film locations around Wellington), +64 4 472 9635
Hobbiton Movie Set & Farm Tours, 501 Buckland Road, Hinuera, Matamata, +64 7 888 1505
Howard’s Mountain Lodge, Caroll Street, National Park Village, +64 7 892 2827
Nomad Safaris (tours of film locations around Queenstown), +64 3 442 6699
Weta Cave, corner of Camperdown Road and Weka Street, Miramar, Wellington, +64 4 380 9361
On Trip Advisor I think the highest rated in is Twizel, largest location in NZ and is Gondor. You can find out more at Lord of the Rings Tour different from the above mentioned site.
I'm late to the party but for anyone reading this later:
Driving to Matamata from Auckland is fairly quick (approx 2 hours) and finding the Information Centre is an easy way to visit Hobbiton. There are brochures and helpful staff in the centre that will ensure you get to try the Hobbit beer and buy a replica ring :).
Related website: http://www.matamatanz.co.nz/Things-to-Do/Hobbiton-Movie-Set-Tour
I think you can go to Glenorchy where most of the war scenes in lord of the ring are photoed