Thank you for all of the helpful information.

If I am reading the table correctly, the maximum cost per minute for an outgoing call within the EU when roaming would be .24 and incoming .07 with outgoing SMS at .08. That seems very reasonable compared to the $1.50/min with my US cell plan. Am I correct here ? Now calling back to the US is going to be expensive anyway but I'll have little need for that and I'll have Skype over wifi for that anyway.

As for data, the max rate looks like .45 per MB which seems very pricey. I also don't need it and will stick with wifi for email and such.

So it seems given the price cap, it really doesn't matter much if I get the SIM card in Iceland and then use it throughout the other countries though most of my calls may be in Greece so getting a Greek one may be a bit better.

I've read that it is cheaper to buy the SIM card once I get in Europe rather than in the US. Is this true ? Any advice or recommendations on where to buy them ? Also given that I'll be roaming, does it matter which company I buy from ? Vodafone seems to be in most of these countries so should I stick with it ?