Most of the time when people think of Canterbury , they focus on its main town of Christchurch, which in the recent times has been hard hit with continours earthquake activity. Not to belittle the importance of Christchurch or its nice gardens and remaining beautiful old buildings, but there is a lot in Canterbury province that isn't just in Christchurch.
Christchurch is a great base to use to explore the surrounding areas of interest, such as Akaroa and Lyttleton. Lyttleton has some of the oldest port buildings left in New Zealand from when it was being intially colonised by Europeans. Unfortunately a lot of these have been damaged in the quakes. But Akaroa and the road out it still remain a beautiful place. The water in the bays are deep blue and the steep drops down to this once old volcanic crater formation are spectacular.
Outside of Christchurch areas, there is the start of the Southern Alps with the famous ski field of Mt Hutt. But more recently the area on the boarders of canterbury and Mt Cook region have become famous for thier role in the Lord of the Rings Triology. Amazing scenery all around the area heading towards the Alps.
There is also Hamner Springs, which is a geothermal hot spot, and a center for some of the best hot pools in New Zealand. Be warned to book early if you are going during peak holiday times as the place fills up fast. There are a variety of facilities on offer if the main pools are too full for you, and the best time I think to go is actually in the evening.
Arthurs Pass which crosses over between Canterbury and Westland, is a spectacular place. It is relitively untouched as its quite a demanding place to live. The national park in this area supports a variety of fantastic hikes, but most amazingly (viewable from the road) is the rock formations. A lot of the amazing rock scenes here are famous from Lord of the Rings, but seeing them yourself is worth the trip. And of course passing through is a great way to see the best part of New Zealand (in my view) Westland.