EDIT: Codes have all run out now
I can confirm this works 100% on Aussie Xbox Live accounts as i did it myself.
Basically enter the blow two codes and timestamps at http://www.chargeupyourfun.com
* bag 1 492105215 (18:08)
* bag 2 565105326 (12:05)
Enter any postcode (including Aussie ones), any name and any email address. You don't need to check your email for the codes as they will pop up after you hit submit, so you can use anything.
What you get is separate codes for The Maw and Toy Soldiers (the first one) and a 2 Week XBL Gold trial. You can do this multiple times with fake email addresses to keep amassing codes to pass onto your friends. Hit back on your browser or enter the same details twice to receive all 3 codes.
For those of you at work or can't be bothering going to your Xbox 360's and manually putting in the codes go to https://live.xbox.com/en-AU and select Redeem Code from the drop down menu and copy and paste your codes to there.
Terms for 2 Week XBL Gold Trials: 2 week Xbox LIVE Gold Membership Trial available for new Xbox Live Gold customers ONLY.
One Xbox LIVE Gold Membership Trial per new customer.
Credit goes to Cheap Ass Gamer. http://www.cheapassgamer.com/forums/showthread.php?t=340718