This isn't very scientific, but I spent about a year of a long distance relationship using OzCall phonecard from GoTalk to call California. I'm not sure how the whole reseller thing works, I'm pretty sure there's 10,000 indistinguishable products designed purely to confuse customers, so it's hard to compare products.
The current rate is 0.5c/minute (half a cent) plus 79c flagfall. I tried out another couple of cheaper phonecards (OzCall was a bit more expensive at the time), but there was issues of network contention, and the delay in the phone conversation was noticable and annoying, so I had to switch back.
Rates are available at:
http://www.cardcall.com.au/en/Rates/Pages/view.aspx?product=AUCCOZcall over 10 years ago
If you haven't already. Get whoever you are calling on Skype (www.skype.com)
Free skype to skype calls, rarely with delay, or if you setup a paid account (not hard) then you can call landlines in Australia for 3 cents a minute.
It is not hard and it is much cheaper than any calling card option.
While I was travelling in Europe I could even find skype on most internet cafe computers so I travelled around with my own headset just incase they did not some provided.
It was definitely worth it over 10 years ago
Skype is a bit expensive. Another way I've been using is Global Call. I downloaded this app from Google Store, I got 30 minutes to call for free already and I've been using it ever since to call not only to the US but other countries as well. The rate is 6 times cheaper than Skype while the quality is comparable. Check it out! :) http://uglobalcall.com/ about 7 years ago