Slack - A messaging app for teams who see through the Earth!
Timezone.io - Keep track where and when your team is.
9mCollab - Collaborate (efficiently) Conclude (fast) Contribute (in the knowledge base)
Time Zone Pro - A beautiful world clock for friends, family, clients and more
Mattermost - Mattermost is an open source alternative to Slack.
Spacetime - Work hour and time zone management for distributed teams.