RoamTheWorldCellPhones.com

Cellphone GSM Frequencies: 900/1800

(This means you will need a GSM cellphone that will work on 900MHz or 1800Mhz to use it in Australia.)

Cellular carriers for Australia

Singtel Optus Limited (YES OPTUS)

Frequency: GSM 900/1800
Website: www.optus.com.au

Coverage Map

Telstra Corporation Limited (Telstra MobileNet)

Frequency: GSM 900/1800
Website: telstra.com.au

Coverage Map

Rogers Wireless Inc

Frequency: GSM 900/1800
Website: www.vodafone.com.au

Coverage Map

If you've used either of these networks or roamed in Australia, please post about your experience and the cost. Feel free to ask questions.