Huckle - Send group messages to people at places
Slack News Feed - Get the top posts from every Slack chat you're in.
CAKE - CAKE provides a SaaS-based solution for advertisers, publishers and networks to track, attribute and optimize their spend in real-time.
Lurchr - Saves all your Slack links, so you can focus on work
Chalk - Chalk is a calculator that tries to do right what others do wrong.
Slack It - A bookmarklet to share links in Slack with one click