Slack

Slack screenshots

Stay in touch with your colleagues and monitor conversations.
Slack 3.1 : Creating Workspace

Alternative downloads

Rocket.Chat
3.0.5
FREE
Web Chat Server, developed in JavaScript.
JBuddy Messenger
3.3.120412
Java-based chat client. If you need to communicate with contacts on several public IM channels simultaneously and don't want to clutter your desktop.....
Potato Chat
2.18.209002
FREE
Send and receive messages and call quickly and securely around the world.