Music has come a long, long way since Napster first interrupted the world's radio stations and made digital music a useful and popular alternative to CD or vinyl.
In this iPod age, teenagers already consider CDs outdated technology, something from their parents' time.
For the new generation of music buyers, music has always been digital and will always be downloaded from the internet.
The parents are left struggling to catch up.
Pandora(www.pandora.com) is a new web music service that might interest all generations. It's a bit like a radio station, and a bit like a jukebox, and a bit like the greatest idea you've ever heard of (if you love music).
Here's how it works: when you visit the Pandora home page, a little music player loads in front of you. It asks for the name of a song, or a musician or band, that you like. You type in a name, then Pandora whizzes off to find music that is similar in style.
It compiles an instant " radio station" of music that it thinks you'll like. And starts playing songs, in decent quality stereo, almost immediately.
The songs are being streamed in MP3 format directly to your computer, so a broadband connection is essential to use Pandora - it simply won't work using a dial-up modem.
Amazingly, this radio station you've created is completely free of advertisements. You just get song after song, along with notes that explain why each one was chosen for your station. Pandora is an offshoot of the Music Genome Project, an ambitious scheme to "classify" thousands of pieces of popular music. Since 2000, a team of volunteers have spent their spare time listening to, and categorising, the work of more than 10,000 different performers.
The resulting database is an extraordinarily deep and detailed exploration of music and musical sounds. Just by giving Pandora the name of one song you like, it can hunt through the database to find songs with similar melodic style, rhythms, and instrumentation.
You can create as many different stations as you like, and even share stations you've created with your friends.
As songs play, you can click on their image in the station playlist to call up a menu of further options, including the chance to buy the song from the iTunes Music Store, or the album from Amazon. Pandora is free for the first 10 hours of listening, which gives you plenty of time to see if you like the service.
After that, it costs a very reasonable 36 US dollars (about £18) for a year's listening.
As a way of creating customised music radio, or of discovering new artists you've not encountered, it's hard to beat.
And compared with many better-known online music subscription services, the price is a bargain.
Writely (www.writely.com) is another interesting new online service, this time for writing and sharing documents. It looks much like Microsoft Word, or any other word processor, but it works inside your web browser instead of running off your local hard disk.
This means you can create and edit documents from any computer that's connected to the net, without lugging a laptop of your own around.
Documents you create in Writely can be shared with friends; you can even both edit the document at the same time if need be.
Writely is a free beta test now, but might start charging a fee when it is officially launched to the world.