What's the simplest—and most affordable—way to make and take calls when traveling overseas? Neil McManus dials up the smartest options

"How much would a ten-minute call to the United States cost from my room phone?" I asked a desk clerk at Munich's Le Méridien Hotel. "I couldn't say," she answered, "but it will be expensive." Not too long ago, calling cards were the best way to avoid sky-high hotel phone bills, but they work only for outgoing calls. For affordability and flexibility, consider some thoroughly modern alternatives, starting with your cell phone.

More than 180 countries (including much of Europe, Asia, and Africa) use the same GSM wireless standard as T-Mobile USA and Cingular Wireless. Before you pack your mobile and charger, though, call your phone company to see if your model will work overseas. If the answer is yes, you have two choices. The first is to ask your carrier to activate "roaming." Roaming will let you make or receive calls on your own phone number as you stroll the Champs-Élysées. That's the good news. The bad news is that, at more than $1 a minute, roaming fees can rival the rates hotels charge, not to mention all the other pesky add-on charges. With T-Mobile's roaming, for instance, your friends can call you for free but you pay to receive their calls, including the messages they leave on your voicemail.

Another way to use your cell phone is to replace its SIM card, the little plastic chip—typically found near the battery—that gives a GSM mobile phone its number. Simply call your service provider and ask them to "unlock" your phone (they'll give you some numbers to punch into your handset). You can then temporarily swap in a foreign SIM card, storing your original chip in a safe place for your return home. You can buy a foreign SIM before your trip from companies such as Cellular Abroad (cellularabroad.com), or wait until you arrive and buy one at a mini mart or newsstand. Either way, you'll pay peanuts. With the Ortel D card I bought for Germany, for example, calls to my office in Philadelphia cost about 12 cents a minute.

If your mobile phone won't work overseas, you can rent or buy one that will. Inexpensive unlocked phones are sold online, or you can even pick one up at a used phone store in the city you're visiting. (Europeans go through phones like chewing gum.) In Munich, for instance, a chain called Second Handy (second-handy.de) sells perfectly good used phones for $30, including the charger. Renting an international phone for a week (online or at the airport) costs about the same—typically $30 to $50—but toll charges can be substantial, ranging from 12 cents to more than $2 a minute for calls to the United States.

Finally, an increasingly popular way to phone home is to make calls from your laptop using Skype or one of the dozens of other VoIP (voice over Internet protocol) services. They all require a high-speed Internet connection and some degree of tech savvy, though Skype is among the most user-friendly. Best of all, calls to other Skype users—even video calls—won't cost a penny.