Imagine free music available 24 hours a day -- not .99 cents -- which you can choose according to the musical style. Better still, the music is accompanied by commentary identifying what it is, and random contextual information, as well as occasional breaking-news, podcast-like audio feeds.

It's called "radio."And just because you're sitting in front of a computer doesn't mean you're not allowed to tune in. In fact, the Internet and the PC is the best thing that ever happened to radio.

There are four basic ways to use your Internet-connected PC as a radio.

1. Streaming terrestrial radio. Sites like Web Radio FM, radio-locator, and live-radio.net let you browse through radio stations organized according to location -- or you can just run a search.

2. Streaming Internet radio. Listening to streaming Internet radio is similar to listening to the streaming feeds from regular radio, except the quality tends to be higher -- better quality sound, fewer or zero commercials and less blather. Sites include KZAM, Warp Radio, and Soma FM.

3. Streaming Satellite radio. If you have a paid subscription to XM or Sirius satellite radio, you can also listen in over the Internet.

4. Your PC IS a radio -- just add the electronics. The site Brando is selling an inexpensive ($20) USB Radio you plug into your PC or laptop that includes an antenna for tuning in local normal radio. You can even save songs to your hard disk.

The Internet brings radio from all over the world -- radio you would never, ever be able to hear otherwise. The best example of what's possible is a really cool site called Clandestine Radio, which is mostly political and propaganda content -- what the editors of the site describe as "clandestine and subversive radio ... where politics, diplomacy, espionage and broadcast media collide." Another stellar example is the BBC, some of the best radio out there, all of it subsidized by UK taxes.