Depending on where you travel to you might want to check out www.callineurope.com . They offer a pay per day blackberry data plan, cheap calls per minute, and a feature that gives you a US # that will forward your calls to your international #. I forward my phone calls right before take off to a 312-XXX-XXXX # and it works great.

Not sure about rates to other areas of the world but for blackberry data (you can tether as well) in the UK it rocks.