The Euro has been the standard currency for all full member nations of the European Union. The EU started with 12 countries, then 15, and now stands at 27 or so, though not all are yet full members (which means accepting the currency, apparently offering social programs and other things).

As it stands now (early 2008), the recently visited Hungary and Czech Republic aren't full members, as some of the requirements aren't sitting well with the countries' population, putting them at odds with the government who may (or may not) be keen on full membership within the EU.

And yes, I have the €50 facing the wrong way both times. There are larger bills, but at current exchange rates, I wasn't going to be getting any €100 or larger notes.