Where should I go?

HI, I will be travelling to New Zealnd and Australia in the summer and would like to take a side trip to a pacific island while I'm there. I've been looking a bit at Fiji (because who wouldn't want to say they've been to Fiji!), but haven't looked into any other islands so I have a few questions:

1) Suggestions of 1-2 of the best/your favourite south pacific islands that could be visited for about 2 weeks total.
2) Is it better/cheaper/more availability to fly out of Australia (which city?) or New Zealand?

Please keep in mind I am on a relatively tight budget and will be toting a backpack. I'm interested in culture as well as surfing and beaching bumming. I am not opposed to tours, although I would like to explore a bit on my own too. Thanks for any help!

Fiji is a good choice, wide range of accommodations. Check out Pacific Blue and other discounted flights, not just Air NZ, Qantas, etc.

Are you talking about northern or southern hemisphere summer?
Polynesian countries are usually closer to and cheaper from New Zealand. Melanesian countries are closer to, and cheaper from Australia.
There are some really good deals now on Skyairworld between Brisbane and Honiara, Solomon Islands. Solomon Isalnds is less developed than Fiji, but great for culture.

Thanks a lot. I will look into flights from those airlines. I am talking about northern summer, so july and august. I would like to maybe fly into fiji, spend a week or so, then fly to another island for a week, then back to wherever i came from (nz or oz).

Air Pacific have a round trip fare from Sydney or Brisbane through Nadi and Port Vila, Vanuatu, to Honiara (although there is only one flight to Honiara a week).
I understand you can stop over in Nadi in one direction and possibly Vila the other. This would allow you to do two or 3 countries. However, you would need to check either the website or a travel agent for the conditions of this one.