Microsoft is currently testing an internal version of Twitter named "OfficeTalk".
The product, made by Microsoft Office Labs, is a cross between Twitter and Yammer according to Mary Jo Foley. OfficeTalk is directed at private and internal communication in enterprises and organizations. Microsoft states that OfficeTalk is in a limited private pilot for research purposes for now. The project is listed as a concept test on Microsoft's Office Labs site.
"OfficeTalk is deployed internally at Microsoft and has seen over 10,000 visitors and hundreds of messages posted daily. We're now making OfficeTalk available to a few customers in a small pilot test," according to a Microsoft spokesperson. Microsoft has not announced any plans to bring the project out of the research phase.