Extracted from a post on the FlyerTalk Travel Technology forum:
I have a Nokia E61 sect-band (800/900/1800/1900/2100mhz) phone with wifi. On the wifi side, I signed up for a free account with truphone.com which has free calls to the US until the end of the year. Where I am on wifi, I'll call free. Where I am off wifi, I can pretty much roam anywhere. Underneath the dashes is a solution I am using when I am in Europe or most of Asia. I originally posted it to a different thread so it might seem a little non-responsive.
I have skimmed through the past eleven pages of the forum post, but if I am hitting things previously covered please excuse me. I travel a great deal and just wanted to share my solutions.
I have a Cingular with their Global Blackberry plan which gives me unlimited Blackberry data access all around the world. I also pay Cingular $2.99 a month for a feature called fast forward which gives me unlimited domestic call forwarding. When I jump on a plane, I literally forward my calls just before the cabin doors shut.
When I get on a European bound plane, I pack a second phone which is basic quad band unlocked phone. I have a Riiing SIM like the prior posters. I purchased for $1 a month a US 800 number from callbackworld.com that forwards to my Riiing SIM at US$0.14 a minute. I also normally use their callback service. I trigger their callback service using my Cingular phone. This permits me to make outgoing calls to the States at $0.14 a minute.
Something prior posters have not focused on is the cost of voicemail when abroad. There is a little covered “gotcha” here. When you are standing in Europe and miss a call or are on the phone, the call gets routed back to the US on a conditional call divert. This means that you are billed for a call to Europe and back again or double the roaming rates. Most people don’t want to turn off their voicemail which means that the carrier charges you at least double for these calls. When I was in Africa, I once got nailed with $15 voicemails -- $5 to call Africa, $5 to forward the call back to the States, and $5 to retrieve the message. I was hit with these charges even when my phone was shut off because I had registered on the Tanzania network and carriers generally hold on to your registration.
Riiing coupled with callbackworld has changed my roaming rates hugely. I used to buy prepaid SIMs for the major countries I visited. I found that despite the slight inconvenience of the callback, this approach is worth it.
I also use a Nokia E61 (not an E62) as my Blackberry (connect) device. It has built in wifi and a voip client. Where I am in a wifi zone, I can make free calls. It is also possible to receive free calls, but that requires more tinkering if you want to always be reached at one number.
By the way, checkout prepaidgsm.net. It is a forum which specializes in roaming on the cheap. Prepaidgsm was favorably cited in a recent EU report criticizing the rates charged for international roaming.