The public beta for OCS is over and it has now gone RTM (as others have posted).
But don’t fret, Microsoft has released fully functional but time limited trial editions of the Microsoft Office Communications Server 2007 and Microsoft Office Communicator 2007.
The downloads (which require registration) are available here: http://technet.microsoft.com/en-us/evalcenter/bb684921.aspx
If you are just after the released Microsoft Office Communications Server 2007 Speech Server then you can use this link – http://www.microsoft.com/downloads/details.aspx?FamilyId=BB183640-4B8F-4828-80C9-E83C3B2E7A2C&displaylang=en
This edition is not time limited, and is fully functional. Yet the use rights are limiting you to developer and test deployments only.
Enjoy these trials.