Android (4.0+): If you tend to keep your music at Dropbox or Google Drive and you like to listen to it on the go, Beat for Android is a music player that's worth a look. The app supports playback from both services, features floating controls over your other apps, supports locally stored music and more.
Once installed, Beat asks you to set a root path for your music, or where you think most of your tunes are stored. From there you can add in-app shortcuts to any folder on your phone's internal storage or SD card (even if you have music stored in multiple folders), to your Dropbox account, or to your Google Drive storage -- anywhere you have music you want to hear. It even sports a software equaliser packed with presets and manual controls for those of you who prefer to equalise your music.
Like many other Android players, most notably previously mentionedSidePlayer, Beat also features persistent, slide-out controls that let you see what's playing, skip forward, go back, or pause without leaving the app you're in, which is perfect if you're surfing the web, chatting, or reading an ebook and don't want to switch apps just to pause the music. Beat is free and available now at Google Play.