Replayify - Create playlists from your most played Spotify tracks
Watch2Gether - Watch2Gether is an app that allows multiple people to watch the same content simultaneously and interact with each other while watching.
Jott - Fast, local, linked notes
Metastream - Watch streaming media with friends
Kindrd - Discover connections between music, movies, books & places
StreamParty - StreamParty is a watch communiry, that allows you to watch video streams in sync with the people you care about, on multiple services.