Just further to Kelster's suggestion above, "Pacific Blue" run budget priced direct flights between the Australian East Coast capital cities of Sydney, Melbourne & Brisbane and Christchurch in NZ, they also do a direct flight between Sydney and Wellington in NZ.
They can be found on the "Virgin Blue" website, (which of course do domestic flights within Australia), that URL is: www.virginblue.com.au.
As for "WWOOF"ing, well, I'm sure they're a very worthy pursuit, and this link may help you: www.wwoof.com.au BUT as an alternative, you may wish to consider "Conservation Volunteers Australia" (website: www.cva.org.au), an organisation I personally (if that's not an oxymoron!) have had something to do with, as a volunteer.
In fact I'm about to take off this coming weekend (Sat 29 May 04) for a three week CVA adventure into far western NSW, after doing a one week "test the water" experience at Easter time in the Nattai National Park south of Sydney.
If it's anything like my first experience multiplied by 3 weeks, then I'll be happy !