Mike ha scritto:

In the next few months we will be in Europe for ten days traveling in
Ireland and Spain. What is the best, most convenient and cheapest way to
call back to the USA? I
would also appreciate the names of telephone providers that worked the best.

I have an account with a VoIP provider that let me call in many
countries (including USA and Italy, my country) for almost nothing.

I use http://www.voipstunt.com

But the same (Swiss based) company (named 'Betamax' like old VCR tapes)
have many other similar services with slightly different tariff plans:

http://backsla.sh/betamax

or

http://progx.ch/home-voip-prixbetamax-3-1-2.html

It works by a small program like Skype on a PC or on any standard SIP
device, like new Mobile Phones, VoIP ATA, VoIP phones.
The drawback is that to call you need a WiFi or cabled Internet
connection, or a high priced 3G Internet connection.
I phoned home for free almost every day wen I was in USA on August 2007
on a 20 days vacation with my E65 Nokia mobile phone.
Many US hotels and motels have free WiFi.
You will find less similar hotels in Europe :-(.
Many have only a WiFi web connection (with paid tokens or cards and
login forms), not a true Internet connection, so no VoIP.
The iperadvertised and ubiquitous Skype is far worse, because you can
call for free only another PC.
With my providers you can call every normal phone number, and also, for
some country, also mobile number for free.
I use it also at home: I will charge 10 euros and the amount lasts for
at least 6 months (you have 4 months of free calls and after, until you
will recharge, 1 cent/minute) and my wife talks very much (both at the
phone and not...).

Ciao, Piero.