What works for freelancers may possibly work for smartphones and PDAs:

Aside from its main function-providing quickly adjustable plugs for fitting into the plugs of 150 countries (what else?)-the 150CADTAAC keeps all its adaptors in its relatively compact enclosure, and comes with a USB port. Yep, it's possible to charge two gadgets at the same time, one through a normal plug, the other through USB.

But perhaps the best feature of this product is its built-in voltage regulator, which protects against power surges. Definitely useful even if you never leave the country. The whole package goes for $40.

PS: 150CADTAAC actually stands for 150-Country Auto-Detecting Travel Adapter And Converter.