Check with your internet service provider first whether the area you live in is supported by them. Then only decide which land line to subscribe to. Note: once you sign up for an internet plan, you are usually locked in for 24 months. If you quit halfway, you will still have to pay a hefty penalty equivalent to the remainder of your contract.
Landline: Basically this is monopolized by Telstra and Optus. They usually will try to sell you a bundled plan, together with mobile phone and internet service. Refrain from bundled plans. These days, some people do not even want to have a landline at home, they just go for naked ADSL (which doesn't require you to have a landline). If you are one of these people, skip this. However, if you really want to have a landline, then go for the most basic plan. Mine is a $20/month plan. My landline is only for receiving incoming calls. I make all outgoing calls on VOIP. Hence my monthly bill is a constant $20.
Internet: Again Telstra and Optus are the big boys. However, TPG, iPrimus, and iiNet are the ones I would go for. See http://bc.whirlpool.net.au/ if you want to know more. TPG has the most cost effective plan. Mine is the $49/month plan with TPG. Even the capped speed is a high 1024kbps, which is highly useable. TPG also has naked ADSL if you so choose.
VOIP: This is for making phone calls over the internet. MyNetFone is the best one around, in my opinion. They have a fully prepaid plan that costs you nothing in monthly subscription. Each call you make to Australia landline anywhere in Australia is 12.5c for unlimited duration. Calls to Malaysia are 3.5c per min. Calls to Australia mobiles are 20c per min with no flagfalls. In comparison, the first one minute of call on a prepaid mobile can cost you up to $1.50. In my opinion, everyone should use VOIP. It will save you buckets.
The only reason I still own a landline is because I am old fashioned. I really ought to just go with naked ADSL.