I maintain lists and groups in several ways.
In Pandora, when I save “an artist” or “a song”, the application itself creates random lists of performers and songs based on the style of the originally selected artist or particular song. So there I have about fifty or so “radio stations” based upon groups whose overall body of work I enjoy, and some individual songs whose mood, melody and feel I would like to see duplicated elsewhere. I love the way Pandora introduces me to new music.
On the iPod that I listen to while I drive I never have a playlist; that’s always set to “random”.
On the computer I maintain a TiddlyWiki (at tiddlyspace.com, and boy am I going to be sorry to see that domain shut down at the end of the year) where I just collect several hundred (so far) YouTube and Vevo and other collections of new and interesting songs and groups and things to look into.
Then there’s always Amazon Music, which I’ve only started to use, and Evernote…