Right now that would be St. Kilda, Fitzroy St. Very cruisy area,
and also full of yuppies. I worked at a cafe there once.. lots of
gorgeous-looking gay (T____T) men in the evenings. At certain times
of the year, u can catch groups of drag queens coming out to
party..
I've only visited Sydney, but I've lived in Melbourne. The latter
is romantic, a little more laid back, european charm.. If you *do*
choose to go there, here are some places that are worth checking
out :
Melbourne CBD incl Chinatown, charming cafes /
bars like
Hairy Canary,
Robot Sushi Bar (they proudly display a
working Atari on premise),
Gin Palace ... HardRock Cafe...
Crown Casino
Shops along Sth Yarra stretch, all the way to
Prahran
Gay/lesbian dance bars, which are among the most
"happening" places at night
St Kilda, the red light district..
Mornington Peninsula National Park : snorkeling,
swim with dolphins
Great Ocean Road, Grampians & beyond : be
prepared to spend a long time on the road, recommend u stay at
least 1 night there (otherwise it won't feel like it's worth the
trip)
Phillip Island : penguins!! 
Yarra Valley wineries : u might find it abit
boring if u're not much of a food/wine lover. Has a good hot air
balloon tour. Be prepared for alot of travelling.
Torquay (on the way to Great Ocean Rd) : Must-go
for shoppers. Many Surf/swim-wear Factory Outlets. Roxy, No Fear,
Ripcurl etc.
Moorabbin : Must-go for shoppers. Another place
that's full of factory outlet. Various brands, most notably Levi's
& Canterbury