While traveling abroad will always require a passport, there are many countries that won’t require a visa if you’re visiting for only a short period of time? In the near future I’ll be making a short trip to Taiwan for family reasons and so I was concerned that I wouldn’t have enough time to apply for a visa and get it in time for my trip. Luckily, if you are a US Passport holder and the trip is for less than thirty days, a visa is not required. This saves me the headache of applying for and hoping its approved in time plus the fees (which are in the neighborhood of $50-100, I’m not sure).
So, if you’re planning a trip, Wikipedia’s US Passport entry has a list of countries and stay periods where a visa is not required . You can save yourself some time and some money by skipping the visa. With the US dollar as weak as it is, you’ll probably want to save that money so you can spend it on your trip!
For a quick reference, in European Union countries the stay period is 90 days, England’s period is 6 months, and for most other places its 30-90 days.