Shtuff Chat - Free Group / Team chat with persistent history.
Sametab - Share company announcements in your coworker's new tab
Meet in Chat - Meet new people. Have fun sharing photos.
Shoutboards - Internal announcement platform for better knowledge sharing.
Kandan - Open Source private chat server. Your own private Chat server in minutes, plus additional features.
Slack - A messaging app for teams who see through the Earth!