AstraChat is an enterprise chat and messaging product that provides privacy and security out of the box.
Slack - A messaging app for teams who see through the Earth!
Mattermost - Mattermost is an open source alternative to Slack.
Cuba - Cuba is a Ruby microframework for web development.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Camping - A Ruby Microframework
Zulip - Chat for distributed teams. Zulip combines the immediacy of real-time chat with an email threading model. With Zulip, you can catch up on important conversations while ignoring irrelevant ones.