Musicolet - Musicolet is a small yet feature-rich offline Music Player for Android.
Magic Playlist - Get the playlist of your dreams based on a song
Poweramp - Music Player for Android
Spotalike - Spotify playlist with similar songs, according to Last.fm
doubleTwist - Music Player for the Internet of Things. Described as the iTunes for Android, doubleTwist brings you music, radio and podcasts everywhere. Free download.
Spotify - Map shows when two people play same song at same time