If you spend most of your time in front of a computer, why do you also need a phone, a cell phone and a PDA to stay connected? Why not do it all with one device - your computer?

That's the idea behind Skype, founded by the developers who unleashed the file sharing program Kazaa on the world. After selling Kazaa (don't blame them for anything recent like the spyware), they created their third-generation peer-to-peer application, Skype, which shares voice streams rather than music files.

Since Intel released the 486 processor a decade ago, computers have had the horsepower to digitize voice. Today, even PDAs have enough power, and Skype offers free computer-to-computer calls with its software. About 55,000,000 software downloads, and more than 20 million unique subscribers testifies that people want this service.

You need a computer connected to the Internet, the free Skype software, and a headset (using a microphone and the computer speakers is painful). Plug the headset into your computer's microphone and speaker connections, start the Skype software, and you can call other Skye users for free. That is, if you know their Skype name or can find them by searching Skype. And if they’re online. And if they're listening.

If you have kids, you know Instant Messaging "rulz." IM also offers Web retailers a quick way to interact with customers.

I'm starting to see Skype buttons on Web sites now, such as this one selling PC phones (http://www.pcphoneline.com/). Everyone selling products over the Web wants more customer tie-in, and a free phone call turns prospects into friends. Skype is cheaper than an 800 number and has some cachet in certain technical fields.

But you don't want to sit at your computer waiting for a call. I don't blame you, and neither does Skype. Take your laptop to Starbucks, along with your headset, and take calls there. Don't want to carry your laptop? Skype works on a large number of Pocket PC devices.

Peer to peer means there are no centralized servers or services necessary, but they are helpful for finding other users. Skype runs a directory of users and tracks your login location and whether you're away from your desk. If you're away for a few minutes, the caller sees a message saying so. If you go away and logon from your PDA at Starbucks, all calls go there. Callers never know where you are, but Skype tracks your location through your logon and online presence.