How the site works is that users can submit URLs from other sites that have music and add them to one of the playlists. This is different from a site like Grooveshark in that users do not physically add the mp3's to the site, only the link. I've been using Stereomood for quite some time now and I've created my own playlist entitled “Study,” which I use for...well when I study. All of the music I listen to on this site is music I would never have heard of before and I enjoy each one thoroughly.
So if you're looking to discover some new music, or just want to try out another site like Pandora, please stop by Stereomood.com and give it a go. I guarantee that you will not be disappointed.