The City of Sydney has a Car Sharing program that offers some 350 cars for very easy, convenient, and affordable self-service car sharing. The rate can be as low as $6 per hour and $68 per day (incl. 150km for free), with insurance and fuel included.
All you have to do is apply with one of the three providers (GoGet, Green Share Car, and Flexicar) with a small joining and/or monthly fee, and you'll get a starter packet containing a smart card. The picture on the right (source) shows the available cars offered by the three providers.
After becoming a member, you can easily book a car by the hour via their website or via phone, and then use the smart card to access the car (lock/unlock door). The photographs on the right shows the smart card reader attached to the windshield for a car I booked with GoGet. You'll have to prepare your own GPS.
The car key is inside the car, and there's a fuel card (pin code was mailed to me after booking the car) that allows the car to be refueled at selected gas stations without paying out of your pocket.
The car sharing scheme seems to be very convenient for people that live within the city and have little need to drive most of the time. They wouldn't need to buy a car, buy/rent an expensive parking space in the CBD, or service and clean the car. And when they do want to use a car once in a while (e.g., visiting nice places in Greater Sydney, moving large items, or looking for a great affordable home to buy in central Sydney), they can easily book a car for a few hours or a few days.