Sprint used to offer a plan called Data Worldwide which you could add on for $40/month on top of an Everything plan. It allowed roaming using one of their GSM/CDMA world phones in over 140 countries. You could even add it for just the time you needed it at a prorated charge. I used it extensively before they got rid of it (as of 2011, you had to be a corporate customer to get it). It was nice having unlimited data on carriers worldwide who didn't even offer unlimited data to their own customers!
