Shtuff Chat - Free Group / Team chat with persistent history.
HeySpace - HeySpace is the only free task and simple project management software with communication and collaboration feature.
Meet in Chat - Meet new people. Have fun sharing photos.
Rivers IM - Simple, fast & secure team collaboration platform
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!