MySocialApp - Seamless Social Networking features for your app
Talkus - Chat with your website users from Slack
Manyverse - A social network off the grid
Slacking Pigeons - Chat in real time with your users directly from Slack
Mastodon - Mastodon is a decentralized, open source social network. This is just one part of the network, run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome!
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.