I'm no crusader for climate change it sort of scares the crap out of me, especially when I start reading this article about the top 100 effects of Global Warming.
There is a bucket load of things you can do around your home, all with varying degrees of cost and effort. Some are simple, like checking with your power supplier to see if they have a green emissions scheme, changing your shower head (this one we need to do) and one we're all forced to do now is use energy-efficient light globes. Others are more involved like installing solar panels. Further things you can do are listed at the World Wildlife Foundation.
The Australian Government also offers some incentives for installing solar hot water systems and roof insulation. So get crackin'!