Facebook group: everyone, like 1.23 billion MAU, is on Facebook. But it has the best ping system for active groups.
Intercom: As powerful as google analytics when it comes to tracking people.
Product Hunt: an online community for tech fanatics & today’s case study example.
Slack: it collaboration on steroids, have real time conversation with your community.
Meetup: world’s large networks of groups
Mention: powerful discovery and audience tool. Get pinged when someone mentions you or your community.