Best Mobile Phone SIM card and plan in Europe?

The question was:

I just found out that my AT&T calling plan in the US can’t be extended to Europe. So I’ll need to get a SIM card when I’m there for a plan that is pre-paid and not a regular recurring billing account. Any recommendations of what you’ve experienced along these lines? Thanks!

Read all the responses on the Camino forum for Best Mobile Phone SIM card and plan in Europe here.