Things that must be plugged in are conspicuously absent from the One Bag packing list; they add bulk and weight rarely compensated for by usefulness. Try hard to eliminate them. If, however, you just can't live without your electric shaver (a small bottle of shaving oil and a razor are much more appropriate), or your hair dryer (think about towel/air drying, or even a more travel-friendly hair style), don't forget that electrical power varies throughout the world.
Most countries use 220 volts AC (alternating current) at 50 Hertz (frequency), though several — including the U.S.A. — use 110 volts at 60 Hertz. Moreover, there are more than a dozen styles of wall socket, each requiring a different type of plug.
Plug adapters and voltage converters are available for all of this, of course (Walkabout Travel Gear is a particularly well-equipped and helpful source of such devices); also check the "Destination" section of the TraveLinks page for an excellent information site). Remember that, when using converters, you must also be concerned with power (wattage) ratings. And some devices (particularly those with motors) are sensitive to the AC frequency, which is not easily converted.
lug adapters can be found featuring all sorts of ingenious constructions, such as the "Tripshell Universal Travel Adapter" (pictured at left), which provides configurable plug adaptation for some 150 countries worldwide. It incorporates a 6A fuse (which means it will handle 660W @ 110V, 1380W @ 230V), L-N surge protector (to isolate sensitive electronics from potential power spikes), 110/230VAC voltage indicators, and child safety shutters. This is a convenient, inexpensive solution if you're travelling to multiple countries, but for a single destination, a simple single-solution adapter will be somewhat smaller and lighter.
Many products are available in compact travel models with "universal" power supplies or multi-voltage settings (though you'll still need plug adapters). And remember: if you carry electrical devices that must be plugged in, you should be prepared for a shortage of available outlets (often in limited-supply/high-demand locations, especially at airports and hostels); consider bringing along a cube tap or the equivalent.
Those travellers who carry laptops (and their attendant power supplies) should know that some low-power electrical items such as battery and cell-phone chargers can be obtained in USB-powered versions, reducing the need to carry additional (heavy, bulky) converters. And those toting a large collection of high-tech gadgetry might find benefit in the wide variety of adapters & chargers at iGo.com. But you can best eliminate the hassles by eliminating the gadgets.
Even if a hair dryer does make a good sock dryer.
All of this notwithstanding, a simple immersion heater is one appliance that many travellers (especially those on a limited budget, trying to avoid restaurant meals) consider invaluable. Place it in a cup of water, plug it in, and in almost no time you have boiling water. This not only kills all disease organisms, it also lets you make a hot cup of tea, coffee, cocoa, soup, etc. You can even cook an egg (bring the water to a boil, remove the heater, drop in the egg, and wait a few minutes). Small, lightweight immersion heaters (such as the Franzus IH100 model pictured here) are inexpensive and available in dual voltages, though you may still need a plug adapter; alternatively, you can buy a new heater locally in most developed countries. Better-quality versions of these have thermostatic shut-offs; with cheaper ones, be sure that the coil is immersed in liquid whenever the unit is plugged in!