The Brown Internal Med program has organized rotations in Kenya and Santiago, Dominican Republic. It's working on establishing a nephrology rotation in China. If you want to set a rotation up on your own, they will support your efforts.
I know that Yale offers great international experiences, as does U. Penn (in Botswana). There are a few others--while it's a bit outdated, AMSA had posted a list of programs offering international experiences.
Remember to ask on your interviews if your salary will continue during an international rotation. As I understand it, since the lion's share of your salary will be paid by medicare/medicaid, it is required that you be in the hospital taking care of medicare/medicaid patients for the hospital to bill for your services. I think it was Emory that got audited several years ago and had to fork up a mouthful to pay back the government for residents missing months due to international rotations. I know that Brown compensates your salary and takes the hit, so to speak. But make sure to ask!
DS