Music for productivity comes in various forms, but if you're the type who enjoys non-vocal electronica in the background while you get stuff done, Focusmusic.fm delivers. Best of all, it's in a simple, minimal interface with few controls and no playlists or other tools to distract you. I've been using the service for a little while, and it's perfect for what it's designed to do: Give you something to listen to while you get some work done.
When I say the interface is minimal, I mean it -- there's a big play/pause button, a forward button and back button, and that's it. You don't even get to see the name of the track that's playing, and there's no playlist where you can browse the songs available and skip around through them. Press play, switch tabs and go back to work.
The service is simple and free, and designed to be minimal on purpose. The addition of a bunch of tools to help you manage music or organise songs would be a distraction (and frankly, you probably already have a service that does that better). Hit the link below to give it a try. I'm a fan of deep house and trance, so the built-in playlist worked well for me. If you're not an electronic music fan though, you won't find much to appeal to you unfortunately.