Do you need a visa in addition to a passport to travel in Europe? We are planning to go to Croatia, Slovenia and possibly Amman, Jordan?
Assuming you are a US citizen, short answer is no. You technically receive an automatic tourist visa for 90 days to any of the European country in the Schegen zone. Doesn't include G Britain. If you are staying longer than 90 days out of 180 continuous days then you will need some type of visa. For GB you are allowed 180 days. As for Jordan, I have no idea. I am sure the Jordanian web site will answer that question.
Go here for current State Department information: http://www.travel.state.gov/travel/cis_pa_tw/cis/cis_4965.html#J Jordan does require a visa, but the State Department says you can buy one at the airport. Always go to the State Department for information of this nature.
Not for Slovenia or Croatia. You'll need one for Jordan, but you can get it at the entry airport for about twenty-five bucks - - nothing to it.