Photostash - Automatically save your pictures from Slack to Gdrive
Magic Playlist - Get the playlist of your dreams based on a song
Google Drive to Slack - Slack notifications whenever you work on Google Drive docs
Spotalike - Spotify playlist with similar songs, according to Last.fm
Slack It - A bookmarklet to share links in Slack with one click
Spotify - Map shows when two people play same song at same time