For free flights from NZ-OZ - you can try Air NZ through Starwood - it is 50,000 points for AKL-SYD in business (note that the flight is only about US$300 return economy) BUT you get 2:1 starwood with a 25% bonus at 20,000 starwood points. So 20,000 starwood points = 50,000 Air NZ points.
As for within Oz, try the red-e-deals at
www.qantas.com.au - SYD - BNE costs about US$50 each way or
www.virginblue.com.au might yeild about US$45 each way but no miles.
Otherwise you can do a Starwood - Qantas conversion (1:1 with 25% bonus) and for 20,000 Qantas miles do SYD - BNE return but I think it is cheaper to pay and get the miles from the flight than transfer Starwood to Qantas.