Last.fm is a free service that lets you type in music artists you like -- and it will serve up a playlist of songs that you will like by those and other artists. It uses a process similar to the collaborative filtering used by Amazon.com’s recommendations: other people who like what you like also liked these other things.

It grew out of (and is most effective when used with) a free software program called Audioscrobbler that build a music “profile” for you and others -- and matches your playlists with those who share your tastes. At last.fm, you can download an Audioscrobbler plug-in for Windows Media Player, and it will keep track of songs you listen to. If you want, it will let you post the lists of your most-listened-to songs on your own web site, and it can share your lists with others. Meanwhile, it keeps getting a better idea of what you like, in order to better make radio stations for you and others.

Or you can just create new stations on the fly, by entering the name of one or more artists. That basically lets you create a new station for every mood

You play the stations through ha a last.fm player, a free and easy download.

Field test: To create my first station, I told last.fm that I like the artists Elvis Costello, Sheryl Crow, and Spoon. The playlist it created began with Wilco’s “Kamera” (an excellent choice), then went to Bob Dylan’s “Not Dark Yet,” Spoon’s “Eveything Hits at Once,” some Elvis C., a Shania Twain reggae song (!?). some Van Morrison, Dido, Velvet Underground, and Jewel. Hey, not too bad overall.

• Tried Last.fm? Weigh in with a review here!