Medicated, check out this post -
Looking for a Game/Looking for more players
You may find one of the groups listed of use. The other thing to do is check out Mind Games on Swanston St in the City. They used to have (I assume still do) a board in the RP section where groups were listed.
Also there are several TOGers in Melbourne that I believe have also been looking for a gaming group. Not sure how successful they have been as yet.