NAB currently charge a fee of $4 plus 2% on foreign cash withdrawls, and 2% on foreign transactions (other than cash withdrawls). However, if you have a NAB Gold account (which has a monthly fee unless you pay in a lot each month), then there are no foreign transaction fees (including no fees on foreign cash withdrawls). So, if you want to take money out abroad more than about 25 times a year, it's worth going for their Gold account.
A normal St George's account currently charges $5 plus 3% on overseas cash withdrawls, and 3% on foreign transactions, so NAB looks cheap... Commonwealth Bank charge a similar $5+3% / 3% fee structure, though they do have a cheaper rate of $2+3% on certain ATMs in New Zealand, Indonesia and Vietnam. Westpac also charge $5+3% / 3%, but they have a larger list of countries where the ATM from a particular bank will avoid you the $5 fee (but not the 3%).
Looks like there isn't a really obvious choice, unless you pay enough in every month to get one of the premium accounts for free. Well, unless you can talk NAB into letting you only pay for a Gold account for only the time you're away!