If you haven't already, check out Australia's very own RedvBlue website hosted by the boys from Microsoft Australia. It is the portal for Microsoft's activities around Halo 3 and raising money for Mission Australia and the Make-A-Wish Foundation. Once there you can find special custom Xbox 360 consoles you can bid on with artists such as 50 Cent, Snoop Dog, Ice Cube, The Veronicas and many more air brushed onto them, with all money going to a fantastic cause.
You will also get the chance to take part in the charity by playing Halo Fore Golf. By scoring the highest score, you will be chosen to nominate a charity of your choice to receive $15,000.