If you support the right for two people to get married regardless of gender, then please respectfully and politely contact your local federal member and let them know.
Those who oppose this have already started up their very effective networks, and we will need to work very hard to counter it.
If you're not sure who your local MP or Senators are, I recommend you use http://www.openaustralia.org.au/ to find out. Just punch in your post code and it will let you know, as well as give you a run down of their voting history.
Do it, DO IT NOW!
This message brought to you by the realisation that I'm going to be rainbow haired soon.