Was there last Dec for 5 days. Stayed in a Hostel type deal on the south coast of the big island (Coral sea?) at a place called the Beachouse. The place was really nice and dirt cheap.
I went on a river rafting adventure with
Rivers Fiji and did the Upper Nauva River. I had seen it on Survivor when a couple of them won a reward challenge. Also heard Chuick Norris has been there and done it.

That was definately the highlight of my Fiji trip so I highly recommend it. A bit pricy but worth every penny.