Hehe, yep, the second one is right.

My mates and I tried a few different types of those cards when we first got here, and it seemed random which shops would be selling which brands - often the place we had originally bought it from didn't have any more.

You can now set Skype up so it renews your account when it starts getting low, which is good if you're forgetful like me.

Agreed. Skype is the way to go.

Purchased a phone card at the main post office but never had the need to use it. While Skype can be very reliable, it's not a bad idea to have a card to fall back on just in case...

I'm using voice777 prepaid card. You can download the software from their website then enter the the code on the back of the scratch card and away you go. I call North America for 295 dong per minute, translating to more then 2 hours of talking to the family and friends for about $2.50 US. The reception is much better the Skype. Cards are available at the second to last retail outlet on the right side of Ly Nam De, a one way street.