Most normal routers - called a G router - have a Wireless Network Speed of 54Mbps (this means the rate at which file transfer will happen between computers linked to the router). These G routers often have a range of about 30 meters, which is roughly 100 feet. The signal will, obviously, become weaker the further away you get from it.
Then you have G+ routers, which have double the Wireless Network Speed (108Mbps) and double the range. These are also more reliable, as the signal reaches further, but it definitely would be wise to set up an enhanced security code if you were looking to get a G+ - during the setup for whichever router you buy, it will prompt you to set up a security code, and what you do is type in a password (let's say you make it "australia"), and the router will translate that into a security code, which will be a mixture of letters or numbers. You can choose a 64-bit encryption (which will be capital letters and numbers), a 128-bit encryption (upper and lower case and numbers), or a 256-bit encryption (upper and lower case, and little and large numbers - though this would probably be unnecessary, unless some darn good hackers live near you).
As for brands, I'm not sure which ones retail out there in Australia, but I have a Netgear G router and it works perfectly - save for a little two-second outage every now and then, but you'll most likely get that with any router. I've also heard very good things about Thomson Speedtouch routers, too. Like has been said in the comments before me, you'd need a wireless USB adapter, which you can pick up from any high-street PC store.
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Then you have G+ routers, which have double the Wireless Network Speed (108Mbps) and double the range. These are also more reliable, as the signal reaches further, but it definitely would be wise to set up an enhanced security code if you were looking to get a G+ - during the setup for whichever router you buy, it will prompt you to set up a security code, and what you do is type in a password (let's say you make it "australia"), and the router will translate that into a security code, which will be a mixture of letters or numbers. You can choose a 64-bit encryption (which will be capital letters and numbers), a 128-bit encryption (upper and lower case and numbers), or a 256-bit encryption (upper and lower case, and little and large numbers - though this would probably be unnecessary, unless some darn good hackers live near you).
As for brands, I'm not sure which ones retail out there in Australia, but I have a Netgear G router and it works perfectly - save for a little two-second outage every now and then, but you'll most likely get that with any router. I've also heard very good things about Thomson Speedtouch routers, too. Like has been said in the comments before me, you'd need a wireless USB adapter, which you can pick up from any high-street PC store.
Hope this has helped!
♥