Tasmania for Xmas - is the go.. for those who love cracks you have Ben Lomond.. for the gun sport climbers there's Star factory and hillwood.. Those into adventure and big routes there Fed Peak, Frenchmans and the Tyndalls..
I'm from the NW Coast so I'm partial to the big easy Rysavy Ridge adventure on Mt Roland.. check out - http://www.thesarvo.com/confluence/display/thesarvo/Climbing+Guides
And I must finish with my favourite White Water Wall.. great location, campsite and climbs..
It also can snow in Summer (highland areas).. so be prepared..