Rainwater tanks
I live in South Australia, often referred to as the driest state on the driest continent. While this is true, the populated areas of SA aren't exactly the Sahara desert, and it does rain here. To save water and get around the current water restrictions in force, a very sensible thing to do is to install a rainwater tank or two to water your garden with. To find your cheap and durable rainwater tanks, visit supatank.com.au.
There are of course some problems in getting a tank installed. I have five tanks, ranging from 2,000L up to 13,500L, and the prices ranged from about $600 up to about $2000. Tanks are expensive, big, and can take a very long time to arrive after you order them. Then you have to get them into your yard - which can be nigh impossible if you have a villa house with very narrow side access - and get them installed.
Polytanks, the big coloured plastic ones, don't need anything fancy in the way of installation. You just sit them on a bed of a few inches of levelled and compacted crusher dust or paving sand, which is sold by the tonne from most landscaping stores. They can be connected to a gravity fed drip irrigation system using PVC pipe, which can be assembled by any DIYer with a hacksaw and some readily-available glue. If you want higher-pressure water to drive a sprinkler system or spray irrigation system, you can connect your tank to a small pump, but be sure that any connections downstream from the pump are made with pressure pipe and glue suited to high-pressure use, and ensure that the pipes going into the pump are the minimum diameter the pump requires, or your pump will burn out.
SA Water has a rainwater tank rebate of up to $800, but for most people it's not useful. You have to have your tank connected by a professional plumber into your house, and it has to be used for something more significant than just as a tap for drinking water. You also need a secondary source of water, such as mains or a bore, which counts out people like me who rely completely on rainwater tanks. Information on the tank rebate can be found here.
For people who are renting, or who are on a budget, you can get 200L barrels from recycling places such as Paramount Browns in Adelaide, just past Gepps Cross. They stand about 4 foot tall, cost between $20 and $50 each and were originally used to import pickled products, so they do smell a little bit funny but they can catch a lot of water from a gutter for a fraction of the price of a rainwater tank, and give you lots of fresh water for your garden. A little hole (with or without a bung fitted) can be drilled into the bottom of these barrels and connected to a gravity feed irrigation system using all standard irrigation pipes and fittings.
Water tank image is taken from Team Poly, who make lots of marvellous plastic rainwater tanks.