Tasmania aside, Australia is so dry that most states are offering big cash rebates for saving water with tanks, shower heads, even dual flush toilets.
Victoria will give you $1000 if you install a large (5000 litre) tank that's plumbed to the toilet and laundry. At the other end of the range, there's $10-$20 for shower heads or $50 for a dual-flush toilet.
South Australia is offering even bigger incentives from 1st Nov 2007. How about a $30 rebate for low-flow shower heads, up to $150 for dual flush toilets, or $200 towards purchase of washing machines with minimum four-star water conservation rating? Call the SA Water Rebates Hotline on 1800 130 952.
There are details about all the council and government schemes on offer nationally at savewater.com.au website.
If you do take the plunge (and the money) and install a rainwater tank, read these two articles published by ABC Radio.
DIY guide to healthy rainwater tanks: http://tinyurl.com/2t4qqq
Tank water (pdf format): http://tinyurl.com/36326t