Our two current contests finish at the end of September, so there's only a few days left. You can still win a Porsche 911 Turbo Wheel for PC or PS3 from Pagnian Imports or a pair of bookshelf speaker kits from The Loudspeaker Kit.
ASUS meanwhile are running an overclocking championship for the next few weeks. If you're thinking you don't have a chance, you might be wrong, because this week's contest is to get the lowest clock speed. Not much Australian representation in the contest so far, but you can find more details in this thread.