For USB charging on North America travel & cruising, I picked up a Belkin travel adapter (3 prongs) with 2 built-in USB charging port & 3 outlets - deeply discounted at local Target store for around $15, has equipment damage protection coverage in unlikely case of voltage spike or surge. I take along the usb cables (mini-usb & micro-usb) that fit most phones in my collection, plus the specialized ones for the digital camera & for DH's iPod, for charging purposes - leaving the charger "body" at home.

For oversea travel, 2 converter plugs that will fit most of the Asian outlets get to go along with the Belkin adapter & I no longer worry if i might need an usb device drivers loaded or reinstalled at foreign places on a guest computer setup.