Tettra - Tettra is a company wiki that helps teams manage and share organizational knowledge.
Photostash - Automatically save your pictures from Slack to Gdrive
Slinky - Your slack links — organized!
Heymarket for Slack - Text and Facebook messaging from Slack
Obie.ai - Access knowledge quicker without leaving Slack
Slack It - A bookmarklet to share links in Slack with one click