Mattermost - Mattermost is an open source alternative to Slack.
B3App - B3App is an event organizing and management platform that helps people throw, run and manage events.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Arcat.XP - Arcat.XP is an Event Management Software that helps organizers, attendees, exhibitors, and sponsors to manage their events with ease from start to finish.
Slack - A messaging app for teams who see through the Earth!
ConventionSuite - ConventionSuite is an enterprise-level event and exhibition management software that is specially developed to streamline, structure, and maximize the entire event planning process.