Cellphones make calls. Smartphones do whatever you want them to, with PDA functions, Internet access and the ability to run hundreds of applications.

For years, the phrase â€PDAâ€phone combo†brought to mind clunky bricks that appealed to only the most connectivity-crazed early adopters. But the latest incarnations of these devices, now known by the more marketing-friendly tag â€smartphone,†are finally fit for the rest of us.

So why do you want one?

Beyond the obvious calling capabilities, smartphones keep your calendar and address book close at hand (and ever more easily synced with your PC), provide access to e-mail and the Web,
let you view and edit Word and Excel documents, listen to MP3s, and even watch movies. Sell the PDA on eBay, and leave the laptop at home.

What makes these phones truly smart is that they enable you to install applications beyond those offered by your carrier, which means hundreds of apps rather than a handful to choose from, and total control over the phone´s functionality. Don´t like the way its address book works? Download a new one. Want real-time flight and gate updates? A calorie counter? A remote for your DVD player? Chances are there´s an app for it.

Smartphones separate themselves in another key area: connectivity. Many allow you to fetch e-mail from your corporate server or personal account, and
several have Qwerty keypads that make replying from the road a real option. And instead of a plodding, text-only version of Web surfing, smartphones have actual browsers that can render sites such as Google and Yahoo true to form.

The trade-off? Beyond price-and these are the most expensive phones you can buy-most are still bigger than a plain cellphone because they have larger displays and a means of inputting text. They also tend to suck your battery dry within a day. And although broadband-like surfing is possible with some smartphones, the carriers are years away from offering ubiquitous coverage with their new high-speed networks, most of which are just starting to roll out.

But these are minor grievances. The phones on the following pages are the most capable portable devices ever produced, allowing you to stay connected 24/7 to friends, family and colleagues and to take care of business anytime, from anywhere. If that´s your thing, follow this four-step guide to find your perfect phone.