Photostash - Automatically save your pictures from Slack to Gdrive
Slackbot Workout - A slackbot to get your team in shape
Heymarket for Slack - Text and Facebook messaging from Slack
Briq for Slack - Engage your team with easy daily recognition
Slack It - A bookmarklet to share links in Slack with one click
SamosaBot by Threado - Free Slack bot to give gratitude to community members