Slackin - Create your own public Slack chat community
Message Bender - Backup and delete all Slack messages in bulk
Slack Archive - Public, searchable & browseable archive of Slack channels
Hamster Pad - A social network built on top of Slack
Islands - Slack for College 🌴
echofin - Echofin helps communities grow, engage and monetize their following in ways no other platform has done so far.