The new version of OCS is Microsoft Lync and you can download it. With more features and a brand new UI, this will be the tool for the people of your organization to Connect and Collaborate.
http://www.microsoft.com/en-us/lync/communicator.aspx
http://blogs.technet.com/b/uc/archive/2010/09/13/introducing-microsoft-lync-the-next-ocs.aspx