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.
JabbR - A chat application built with ASP.NET and SignalR.
Slack - A messaging app for teams who see through the Earth!
Smarsh Instant Messenger - smarshIM Mobile is a free application download that requires a paid account on the smarshIM service...
The New Dropbox - Enterprise software portal for team collaboration