VOIP telephony to make U.S. calls while in foreign country

I'm visiting my brother in Panama, a great country -- but unfortunately one in which my cellphone will not work.  But I came prepared for this situation.  Among the things I took with me was my Packet8 phone, which is an internet-based phone system (i.e. VOIP, or 'Voice over IP').  For $20/month I can make and receive unlimited calls in the U.S. and Canada. I have been using this phone for my work.  I have a New Orleans area code, and I can set the phone up so that it rings simultaneously to my cellphone (where I can take the call if I want).

But since my cellphone doesn't work here that's not useful right now (although it's very useful when I'm in New Orleans).  Anyway, I set the Packet8 phone up here by attaching it to my brother's router and --bada boom bada bing-- my 'landline' phone works like a charm.  Another thing that works like a charm is Skype, the free VOIP phone system that lets you use your computer to make and receive phone calls.  I can call anyone in the United States for free.  Skype works with Macs and PCs.