My transatlantic call with my little sister at Smith College in Northampton, MA, starts with her recurring complaint about the campus food. This week, it seems, there's a shortage of fresh fruit. Normally, as the long-distance seconds tick by, I'd be tempted to ask her about more serious issues. But this time I'm happy to listen: our hour-long call, placed over the Internet from my computer in Riga, Latvia, to her computer in Northampton, is using a free program called Skype and is costing us nothing.

When I start up Skype to call my sister, the software links my PC with the computers of other Skype users who also happen to be online. In this case, one of them is my sister, 6,500 kilometers away. Our voices are broken into digital packets that hopscotch from computer to computer until they reach their destinations, where they're reassembled into astonishingly clear audio.