http://ocsphoneguy.blogspot.com/, draws our attention to an incredible FREE OCS to SIP Phone integration. This integration allows you to connect Office Communicator to a SIP phone to make PBX calls directly from Communicator! While this integration is with snom phones something like this could be done with other standard SIP phones also.
Jan is very passionate and knowledgeable about OCS and I recommend you checkout his blog:
Here is the company website directly: