The latest app from doubleTwist lets you take advantage of all that online storage you're (maybe) sitting on. CloudPlayer does what the name suggests—it plays music from your cloud storage. Just upload your tracks and plug in CloudPlayer.
The app supports Dropbox, OneDrive, and Google Drive. You would, of course, be able to simply navigate to the file locations of any song in one of the official clients for these services and play it, but CloudPlayer operates like a traditional music player. You get high-resolution album art, playlists, offline sync, and a 10-band EQ. It's sort of a roll your own Play Music option.
The utility of this app relies upon making sure you have enough cloud storage in one of these services to accommodate all your music. Should you go this route, CloudPlayer has support for Chromecast and AirPlay out of the gate. Both those features are part of the premium version that costs $4.99 via an in-app purchase.