Australia Day is rad, definitely my favourite public holiday.
There is no religious impetus for it, it's guilt free (noone died for the holiday) and it's in the middle of summer.
Thongs, wife-beaters and stubbies are the attire of choice, while you kick back, drink some beer (though perhaps NOT keeping the beer in the spirit of the holiday—Fourex and VB suck my balls!) and chuck some prawns on the barbie—gold!