I'm with iprimus. Costs me around $49 per mth, unlimited d/l but the connection speed drops to 256k after 500mb in any given month for the remainder of that month, which isn't so bad if you're an medium-level user. Got the modem free, also (I think it was worth a $250 back then). Not sure if that's because I have my phone with them as well.
I reckon Optus is shite customer service-wise, too. (Had my mobile phone with them at one stage.)
I am told TPG is worth looking at but I'm in no real hurry since I'm pretty happy with iprimus.
I sent myself an email from work with a few other providers and prices/packages a few months ago. PM your email address to me if you'd like me to forward it on.