There are some cards that are supposed to work in multiple countries. I've never tried them because I've heard it's iffy whether you will actually find a phone that takes them after you're out of the first country.
I've only used the one country cards (meaning you can only call from one country to anywhere). They worked good and save a ton of money over other options. I use it up before crossing the border and buy another card in the next country.
I'm debating whether to get a cell phone only because I call for a room at my next destination mid-morning. It would be nice to make the calls as I'm traveling without planning a stop at a phone booth.
I then have to decide whether to use my phone or buy a European one. My cell phone will work in Europe. At a dollar a minute, however, the bill can add up pretty quickly.