Well, Kevin Rose is one of the founders of Digg, and has come out with a brand new service called Pownce. He has quite ambitiously sent the company out to the ever challenging Internet marketplace. Pownce is a new network of instantaneous client that offers the functionalities of Twitter/Jaiku, allowing the sending of messages, files and events with the other users.
This new system has developed its client on Adobe AIR(Adobe Integrated Runtime ), and hence it is necessary to install the AIR to your computer. Since AIR is currently only being available for Windows and Mac. If you have Linux - you will have to hope just a little bit.
At the moment the service is in closed beta, and can only be accessed by means of an invitation.