Spotify Free is free, obviously, although it has its limitations.
Spotify Premium is free for the first two months, you can always switch to the Free version before that.
There's also Spotify Unlimited, it's hidden on their site, but I could downgrade to it last summer, €5/month. Dunno if it still works.
http://www.spotify.com/se/account/subsc ... =unlimited
Yes, I'm talking about Spotify as if it's the only thing that exists, but that's because I've used it for a while.
There are of course other alternatives, but I have no experience with them.