First-time buyers of iPods and MP3 players are often surprised to discover that their expensive little music gadgets lack an obvious feature: a radio tuner. The conspicuous absence of a built-in radio option on many digital audio devices raises a serious question for consumers raised in the era of old media: Has digital killed the radio star?

Indeed, a new craze called podcasting is making its way to digital music players everywhere and threatening to make radio obsolete. "Podcasting," or iPod broadcasting, is a new way of using the Internet to distribute pre-recorded audio programs to mobile audio devices such as Apple's wildly popular iPod. Users download individual files called "podcasts"--recorded episodes of varying length made by people ranging from experienced pros to wannabe DJs--which can then be listened to on iPods and MP3 players while driving to work, exercising, or making dinner.

Podcasting has two key advantages over traditional radio. First, it enables almost anyone to produce his or her own radio show. Using a computer, mic, and broadband connection, a person can create a broadcast or infomercial and distribute it via popular podcasting sites like Ipodder (ipodder.org) or Podcast Alley (podcastalley.com). Second, podcasting gives consumers unprecedented control over the content they wish to hear. Users can subscribe to thousands of free and fee-based podcasts, and each new episode is automatically delivered over the Internet to their digital audio players.

What do podcasts sound like? The first podcasts have been largely entertainment-driven, with content ranging from the lunatic rants of school kids to the slick corporate programming of Infinity Broadcasting. But other uses are emerging. For marketers seeking new ways to reach customers through technology, podcasting is more than a new form of entertainment--it's an unprecedented business opportunity. Podcasts may soon be used as a way to support existing business, spin off ancillary business, or create entirely new businesses. The same digital audio devices that enable music fans to listen to their favorite songs by U2 and Snoop Dogg also create channels through which savvy marketers can develop ongoing relationships with customers every time they put in their earplugs.