Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.
Photostash - Automatically save your pictures from Slack to Gdrive
Palaround - Meet people you should be friends with.
Google Drive to Slack - Slack notifications whenever you work on Google Drive docs
Babble - A more personalized social network
Slack It - A bookmarklet to share links in Slack with one click