Slack Overflow - A programmer's best friend, now in Slack.
Google Drive to Slack - Slack notifications whenever you work on Google Drive docs
GitCommands - An interactive reference tool for Git commands
Kissflow - Kissflow is a workflow tool & business process workflow management software to automate your workflow process. Rated #1 cloud workflow software in Google Apps Marketplace.
GitHub + Slack Integration - Full visibility into your GitHub projects right inside Slack
Heymarket for Slack - Text and Facebook messaging from Slack