Slack Overflow - A programmer's best friend, now in Slack.
Moz Link Explorer - Search engine for links Perform competitive website research.
GitCommands - An interactive reference tool for Git commands
MetaTagsTool.com - Meta Tag Analyzer, Simulator, & Generator
GitHub + Slack Integration - Full visibility into your GitHub projects right inside Slack
OpenGraphWiki.com - Open graph generator and simulator. Test or generate open graph tags for any web page.