As wireless phones become increasingly sophisticated and laptop computers get smaller and lighter, the gulf separating them grows ever narrower. Somewhere between the two are highly portable mini-PCs capable of running Windows XP or Vista yet light enough for you to operate standing up.

Among notebook PC makers, Sony and Toshiba now have models that are less than an inch thick. And established manufacturers of handhelds such as Samsung and HTC, along with upstarts like FlipStart Labs and OQO, are creating pocket-size PCs known as ultramobiles. Many are built around Intel’s technology. (The company even released a platform this spring called the Ultra Mobile.) Its current chipsets are just as powerful as earlier versions but consume far less energy, which means the devices using them can run on smaller, lighter batteries and won’t cause ligament damage if you’re forced to carry them around all day. Most ultramobiles come standard with WiFi and broadband cellular, as well as Bluetooth. Many also feature drop-detection technology to minimize damage if they’re accidentally mishandled.

Here’s a roundup of some new devices for your carry-on bag—or coat pocket.

1. OQO Model 02
Price: $1,299
Size: 5.6 inches by 3.3 inches
Weight: 1 pound
Pros: An upgrade from OQO’s Model 01, the 02 is one of the smallest devices capable of running Windows Vista. It also has a faster processing speed than the original, a 5-inch screen (with stylus), and a four-hour battery life.
Cons: The keypad will cramp your thumbs.

2. HTC Shift
Price: $2,000 (final price not announced as of press time)
Size: 8.5 inches by 5 inches
Weight: 1.8 pounds
Pros: The Shift, due in stores by the holidays, has an innovative slider-style design that lets you access the keypad by tilting the touchscreen.
Cons: HTC has extensive smart-phone and palmtop experience, but the Shift is its first ultramobile.

3. Sony Vaio TZ
Price: $2,200
Size: 10.9 inches by 7.8 inches
Weight: 2.7 pounds
Pros: The Vaio TZ comes with an 11.1-inch widescreen display, and its media players for DVDs, photos, and music are accessible in standby mode, circumventing boot-up delays. Sony also offers a model with flash-based memory, which loads applications faster than laptops with hard drives.
Cons: That flash version is pricey—about $3,000.

4. Toshiba Portégé
Price: $2,150
Size: 11.1 inches by 8.5 inches
Weight: 2.4 pounds
Pros: Among the world’s thinnest laptops at just three-quarters of an inch, the Portégé includes a DVD burner, a 120-gigabyte hard drive, and a battery that lasts all day.
Cons: No mobile broadband, so you need to buy a PC card separately.

5. Roper Mobile SwitchBack
Price: $5,000
Size: 7.5 inches by 5.5 inches
Weight: 3 pounds
Pros: Rubber and magnesium casing make the SwitchBack both rugged and waterproof. It can be fitted with more than 20 BackPack add-ons, from a basic digital camera to a credit-card reader.
Cons: It’s the heaviest and most expensive of the devices shown here.