Nelson: There's not a whole lot to do in Nelson itself, but its location is great. To the north you have Abel Tasman, which you can kayak, hanglide, hike, and skydive. To the southeast there's Marlborough, which is known for its awesome wineries. Its also near the coast and has the best weather of the south island.
Queenstown: The big daddy. Don't miss it. I only got 3 days there, but if you can do like 5. Leave 1 activity a day, and leave some room for some drinking. That wallet is gonna hurt, but its worth it. If you wanna relax, go to Wananka. Super bonus is its close to Milford Sound, which is amazing.
Raglan: This is a must see. Its location is remote, just west of Hamilton. About 2 hours outside of Auckland, its the perfect beach town away from everything. It is the perfect place to unwind, forget everything, and grab a surfboard. If you wanna relax, go here. Each day will be better than the next.