Slack - A messaging app for teams who see through the Earth!
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Confluence - Confluence is content collaboration software that changes how modern teams work
Mattermost - Mattermost is an open source alternative to Slack.
Flock - A faster way for your team to communicate
Sharepoint Online - SharePoint is a secure place to store, organize, share, and access information from almost any device.