One of the best features of the late, lamented Audiogalaxy music sharing system was the suggestions it made of music you might enjoy. If you looked at the page for a particular artist, it would also offer artists that were similar.
This matching process wasn't done by humans but automatically calculated based on what the users of the system actually had. So, for example, Metallica fans might well also have a lot of Sepulchura and Slayer, so that suggestion would be made. Other suggestions were less close stylistically but seemed to work based on taste. It was one of the best ways to discover new music.
Unfortunately Audiogalaxy has gone the way of the dodo, thankyou music industry (another set of dodos, just hanging on a bit longer). The future for all the excellent things Audiogalaxy did seems to be to decentralise it. Decouple the file sharing system from the inventory of music and perhaps decouple that from the similar artists functionality.
This is where a new system I've just discovered comes in. Audioscrobbler works as a plugin to your favourite audio playing software and reports what you're listening to into its centralised database. It can then offer suggestions of music you might like. Yes there are both Windows and non-Windows plugins. Pretty cool!
A side-effect of this is that you can see what I've been listening to here.