As prices have tumbled and the capabilities of portable PCs have grown, laptops have taken an increasingly large part of the retail PC market.
A handful of market leaders have emerged, among them Toshiba, IBM Lenovo, Dell, HP and, of course, Apple Computer.
But there is still plenty of choice in the market, including specialists such as Alienware, the Florida-based company that has carved out a niche with powerful portables aimed at the games market, Panasonic with its "ruggedised" Toughbook machines and a handful of companies making tablet-style portables.
Now that Intel and AMD have largely abandoned the "Megahertz" race in favour of other differentiators, it has become relatively easy to set out the basic specifications for a general purpose portable - 1.4Ghz (Gigahertz) processor, 256 or preferably 512Mb (Megabytes) of RAM, 40Gb (Gigabytes) or larger hard drive and super-bright colour screens are now all fairly standard, along with WiFi and Bluetooth wireless network capabilities.
Beyond these basic requirements, the options become largely a matter of personal choice. Among these features are widescreen LCD panels, ideal if the machine is likely to be used for watching DVDs or other multimedia content. In this case also look for the "instant on" feature found on most Toshiba laptops, such as the Qosmio G25-AV513, and a growing number of other machines.
If the machine will mostly be used in one place - or transported occasionally - consider a desktop replacement machine with a full set of optical drives and flash memory card readers that make it easy to transfer images from digital cameras.
Now that most of the premium associated with Microsoft's Windows XP Media Center Edition has gone, it may also make sense to look for a portable running MCE.
At the other end of the size spectrum, a sub notebook machine such as Toshiba's Libretto, Sony's Vaio VGN-TX610P/B or the new Fujitsu LifeBook 1500d could be ideal, but check out the battery life before buying - it often makes sense to buy a second or extended battery that will deliver at least five hours of computing time.
For the ultimate in portability, OQO's Model 1 is a full function PC running Windows XP in a pocket- sized package, or consider using a Palm or Windows- based PDA (personal digital assistant) with a portable keyboard.
Tablet PCs - portable machines that run Windows XP and have touch-sensitive screens - remain a small part of the market. I particularly like some of the lightweight "convertible" tablets that have appeared this year, including Lenovo's ThinkPad X41 and Fujitsu's 1510d, both of which can operate in standard notebook mode, or like a writing slate with an electronic pen.
At an ever more basic level, most of the applications and private data that mobile professionals need can now be carried around on a Flash memory USB drive that can be plugged into virtually any PC.
Portable PCs and communications go hand in hand so it may also be worth considering one of the new PCs such as the Sony Vaio VGN-T350P or the Lenovo ThinkPad Z60t, which both come with built-in WAN (wide area networking) capabilities designed to work with 2.5 and 3G wireless networks.
Over the next few months these and other machines with 3G wireless networking will become much more widely available but if you cannot wait, make sure you buy a PC with a PC card slot that uses a 3G data card.
Home storage and media distribution
As the volume (and value) of digital content stored on portable, home and office PCs has grown, so has the need for easy-to-use external storage and systems that can help distribute that content around the home or office.
Maxtor's family of OneTouch external drives set the benchmark for external storage and data backup, but all the main hard drive and networking equipment vendors - including Seagate, Netgear, Linksys, Buffalo, SimpleTech and Seagate's recently acquired Mirra unit - now offer external storage devices designed to manage and in some cases distribute up to 1Tb (Terabyte, or 1,000Gb) of data.
Some of these vendors also sell "media gateways" that are designed specifically to make easier the sharing of digital content over a wired or wireless home network. Others sell devices designed to integrate with traditional hi-fi and home theatre component systems, enabling users to listen to digital music through a stereo system or view digital images on a TV screen.
One of my favourite digital home audio systems is the Sonos Digital Audio System - a wireless digital audio distribution system that lets users access and control digital audio content stored on a PC or external hard drive from any room in a house using a stylish wireless remote control.
There is also an expanding range of iPod add-ons from companies such as Griffin, Kensington, Bose, Belkin and Xitel that are designed to enable iPod owners to listen to their music at home or in a vehicle.
