HeySpace

HeySpace is an entirely free collaboration software consists that consists of two major features: task management and advanced, powerful chat. HeySpace is the place you move the work forward. You can do everything in the card. Chat with co-workers, write rich text documents, tag, mark progress, set due dates and other useful things. The cornerstone of HeySpace and the most frequent thing you do - communicate with people. Send a message and see if they read it, create tasks from messages - if somebody says something important, make a card out of it and it will move to the cards list.

It's just one click. Suprisingly useful!