I've always wanted to visit Australia. I live in a state with over ten million people alone and can't imagine only twice that number having an entire continent to themselves! I also have a summer birthday and would love to visit anywhere in the southern half of the world where I could have a snowball fight on my birthday, although my only real chance I think would be in the southeastern mountains.
I'd have to spend at least a month there. I'd want to spend a few days in each of the big cities, plus tour around seeing the Outback and the rainforests/tropical areas in the north.
Of course if I could sneak in a week on each of the New Zealand islands, I might as well do it while I'm down there. It would also be my chance to possibly see Antarctica as a day trip.