Just this past week, I found a couple really cool music sites, Audioscrobbler and last.fm. They're closely related, and in fact share the same user database. Basically, what the two sites do is keep track of the music you're listening to, and make suggestions on new music that you may be interested in. Last.fm provides a better user interface, and also provides the option of listening to streaming audio of suggested tracks. Audioscrobbler provides a plug-in for various audio programs, including Windows Media Player and iTunes.
Anyways, what the sites do is keep a simple track database that allows an algorithm to estimate a person's listening habits. There are three ways for a user to edit the track database: (1) manually add tracks by going to the track webpage in last.fm (for example, "Always" by the Newsboys) and clicking on the add button; (2) listening to the track in a media player with the Audioscrobbler plugin installed; or (3) listening to the track on one of last'fm's stations and reacting to it (either by listening through it, skipping it, or banning it). You can check out my stats here -- most popular bands, most popular tracks, and last ten tracks listened to.
The algorithm then takes all user track databases and compares them in order to determine 'neighbors'. A person's neighbors are those whose track databases are most similar to that person's own database. For example, my closest neighbors right now are thetamind and nshane. As you can see by their stats, thetamind listens primarily to softer Christian alernative (well, softer than me, at least), while nshane listens to harder music, primarily secular but some Christian stuff. My full neighbors list can be seen on my stats page.
From neighbors, the algorithm is able to do a couple things. First, a customized radio station is created on last.fm, pulling tracks from one's neighbor's track databases. Second, individual track recommendations are made by triangulating based on neighbors -- if there is a music track listed on many of your neighbor's track lists but not on yours, there is a good chance that it is a new track to you that you will like.
CHECK IT OUT! Join if you can, and then add me as your friend. And let me know that you've joined the site -- it seems like I'm not notified when someone adds me as a friend, so I won't know you've joined unless you send me some sort of message.
Once I understand what Musicbrainz does, I'll probably write a post on that, too.