international calls

i did some research for calling to/from vn. of course people on /. have already asked this question. but here's what i found after skimming through the comments:

• onesuite for calling from us to vn, phonecard
• pingo from us to vn, phonecard
• sipphone pc2phone
• iconnecthere pc2phone
• skype pc2phone or pc2pc
• vonage phone2phone, or pc2phone with softphone