Top tip: Go for USB-based charging wherever possible
Gadgets like the iPhone and iPod include their own USB-based charging cables. But most other mobile gadgets can also be powered via USB. This list includes nearly all cell phones and Bluetooth headsets. (The big exceptions are laptops and portable DVD players, because their power requirements exceed USB's 5-volt load.) So the first thing you'll want to do--after verifying that the device in question is chargeable via USB--is to get a matching USB charge cable.
You'll need proprietary USB charging cables to match the ports on the Nintendo DS/DSi, for instance, but many other devices are finally starting to use standard connectors--mini-USB on most BlackBerry phones, micro-USB on the Palm Pre. (Kensington, for instance, makes retractable USB Power Tip USB cables for a variety of phones and portable devices.) On the other hand, the USB ports on some devices are for data transfers only. Other devices--such as the Amazon Kindle and Sony Readers--can be recharged via PC USB ports, but not third-party USB accessories. You may need to consult your manuals--or do some trial and error experimentation--to make sure USB charging is even possible or has limitations on a given device.
Once you've got the necessary cables and you've verified compatibility, you're ready to charge everything via USB. You could use your existing iPod/iPhone charger, but its single USB port means you can only charge one device at a time. Thankfully, there are plenty of products that have two or more USB ports on a single wall-wart.
If you only need to juice up two devices, something like the Belkin Dual Rotating Charger (bottom middle) is a good choice. In addition to travel-friendly foldable, swiveling power prongs, it includes three charging cables (iPod/iPhone, mini-USB, and one that works with earlier iPod Shuffle models), and it's widely available for less than $25. (The similar Griffin PowerBlock Dual Universal--at the top left--is cheaper, but it doesn't include any cables.)
If you need to double that capacity up to four ports, you might consider the Kensington 4-Port USB Charger. But another alternative is the Lenmar ACUSB4 AC Travel Adapter (top right)--it's basically the same as the Kensington, but it includes snap-on adapters for international plugs. I've been using it to charge multiple phones and iPods on my desk for the past several months, and it's worked perfectly.
Want power in cars or planes that use a standard cigarette lighter socket? Get a two-port USB adapter from Belkin (right), Griffin (left), or Scosche (center). Each of them has two USB ports. (Again, we lean toward the Belkin because it's the only one that includes USB cables: one mini-USB, one iPod/iPhone.)
Whether it's in a hotel room, an airport lounge, or a coffee shop, AC outlets are like gold. But it's hard enough to find just one--might as well make the most of it. That's where a mini powerstrip comes in. Monster's Power To Go models turn one outlet into three (the black model shown above), four, or six. and their short cord folds up perfectly for easy storage. There's a version with a built-in USB power jack as well. The Belkin Mini Surge Protector (pictured, on the left) is a tad bulkier, but it offers three AC outlets, two USB charging ports, and it protects connected equipment from power surges (complete with a $75,000 insurance policy). Kensington offers the similar Portable Power Outlet as well. All are available for less than $30.
This one is obvious, but we'll mention it anyway. If you're leaving the laptop powered up overnight, you can always use it as a makeshift USB charger for a couple of other devices. Some newer Toshiba laptops even have a USB pass-through mode, so USB charging works even when the laptop is powered down. Some third-party aftermarket laptop AC adapters also include a USB port or two for charging extra gadgets as well.
There's nothing worse than losing an adjoining AC power outlet just because a fat wall wart is taking up too much real estate. If you've got such an offender, consider a mini-extension cord. They go by several names, but packing one of these "Power Strip Liberators" in your bag can often be a lifesaver. Likewise, anyone with a MacBook might go for the Brian Lam cord mod, which offers the same sort of advantage. (OK, this one is more general advice than a travel tip--but we threw it in anyway.)
Most gadgets are world-ready--but check to be safe
Traveling overseas? Good news: nearly every portable gadget these days is world-friendly. To double check, just look at the power supply: if it says it accepts 100-240V / 50-60Hz, it should work with pretty much any AC grid on the planet. That means you don't need one of those heavy step-up/step-down voltage converters. Instead, all you'll need is an adapter plug for the different outlet shape. You can go with country-specific ones, or get an all-in-one version with multiple prongs that'll work nearly anywhere.
Remember: These power accessories can work in tandem. Rather than buy two or three international adapters, just snap one onto that mini powerstrip, and you should be good to go. You can also avoid misplacing them during travel by leaving them linked together.
Whether you've got your own PC with you or not, it never hurts to have a USB thumb drive handy for sharing files or moving documents or media files in a pinch. We love the Lacie IamaKey drive: the metal design is more durable than plastic USB drives, and leaving it on your keychain means you'll always know where it is. About $30 buys you 8GB of storage.
Coffee shops may or may not be starting to crack down on patrons who use their power and Wi-Fi while they nurse a single mug of java for hours on end. But savvy travelers can find power in more and more places. Web sites like SeatGuru will tell you exactly which seats on which airlines and which planes (e.g. Boeing 767, Airbus A320) have power outlets under the seat (it'll also tell you if they're standard three-prong outlets, automobile-style 12-volt outlets, or other). Meanwhile, newer airlines like Virgin America make it even easier, guaranteeing standard AC and USB power outlets at every seat.
Updated:Caption:John FalconePhoto:Screenshot by John P. Falcone/CNET
...but be ready to go off the grid
Of course, even the most seasoned travelers will find themselves occasionally off the grid. Many popular phone models have snap-on power boosters to extend the battery. But you'll get greater flexibility from a USB-based rechargeable battery module. There are several available, including the Kensington Portable Power Pack for Mobile Devices (left), the Duracell Instant USB Charger (center), and the Energizer Energi to Go Xpal XP2000 (right). Charge them up via USB (from a wall adapter or a PC), then use them to juice up any USB-friendly gadget. Perfect for transoceanic flights.