Clearbit for Slack - Send all signups directly to a Slack channel
MisterJack - Make and share playlists
Photostash - Automatically save your pictures from Slack to Gdrive
Designers MX - Curated playlists by designers, for designers.
Slack It - A bookmarklet to share links in Slack with one click
Monolist.co - The command center for engineers. Tasks, pull requests, messages, docs — all in one place