Slack

All your team communication in one place, instantly searchable, available wherever you go. That's Slack.* Real time messaging, file sharing, supporting one-to-one and group conversations* Powerful search and archiving, meaning no one is ever left out of the loop* Dozens of integrations with tools including: Dropbox, Asana, Google+ Hangouts, Twitter, Zendesk* New integrations and features added frequently* Inline images and video, with rich link summaries giving context without leaving the app* Instantly synced across all devices* Configurable notifications for desktop, mobile push and email* Scientifically proven (or at least rumored) to make your working life simpler, more pleasant, and more productive.Slack is free for an unlimited number of users, and an unlimited amount of time, with upgradable plans for extended message history, unlimited integrations, file storage and customizable data retention policies."There are two types of people in the world: those who have never heard of Slack, and those who can’t imagine life without it." - The Guardian"You can tell that the team that designed it really took their time focusing on the little big details. It’s simple to use and powerful at the same time." - User Experience Rocks