Mattermost - Mattermost is an open source alternative to Slack.

Chili Piper - Chili Piper is an intelligent calendar for Sales teams, to book their own meetings or set appointments for other teams.

Slack - A messaging app for teams who see through the Earth!

Geekbot - Discover how to organise asynchronous stand up meetings in Slack and keep your team synced using Geekbot. Start your free trial today!

Espresso Chat - Productive conversations start here

Doodle - Make meetings happen. With Doodle, scheduling becomes quick and easy.