JUST Mobile has just lowered its rates but kept the best conditions. No flag fall, 30c/minute (charged per second), 15c per SMS and credit has 180 day expiry. The minimum recharge is now $15. They use Vodafone's network. Oh and they have 20% off specials occasionally.
I'd recommend them, in fact our whole family is with JUST.
Mod - Added merchant and network details to the title.
PS I corrected my poor maths (cents/second)
http://www.virginmobile.com.au/mobile-plans-pricing/pre-paid…
10c/min (charged per 30 seconds)
10c SMS
45day expiry
25c flagfall
and i think there were cheaper ones somewhere