the world's smartest travel social network
You will find many on my website: www.australianregionalfoodguide.com.au Simply go to the state you are visiting and hit the Accommodation button. Because it is a 'regional food' website these places have been chosen because they serve home-grown or local produce in the meals they serve. Good luck and have a great trip.
In New South Wales:
There are two farmstays very close to Sydney which I know are good.
Both offer accommodation and food and a variety of farming activities and displays.
Both are large tourism operations with day trippers and programs etc.
If you want to visit a small working farm and stay somewhere quiet you'll need to get right away from Sydney.
Barcoos Barn Farmstay http://www.barcoosbarn.com.au is at Bathurst, about 2 1/2 hours West of Sydney.
It's a small place, a genuine working farm that has horses and chickens and peace and quiet.
For an adventure tour that includes a farmstay Aussie Farmstay and Bush Adventures http://www.aussiebushadventures.com.au/ offers 4 day tours in the Central West of NSW and the Blue Mountains which stay at an historic sheep farm one night. There are draught horse and shearing displays and a great night of campfire entertainment.
Is there a particular area in Australia you are interested in?