Why does it specifically have to be an Australian group?
If you're looking for the opinions of people relating to religion and the like (but aren't restricting it to Australian members), convert_me does a pretty good element of debate.
But it's unclear exactly what type of questions you're trying to ask (from the quick skim of the comments, I haven't figured out whether it's "Help me find xyz Christian-related material?" or "What do you guys think about...?" - but I may have missed where you said so).