Have you heard about the new release of Office Communications Server? The new name will be Lync Server 2010 and if you want start playing with the new product, then this Lab Deployment doc is for you.
A step-by-step, how-to document you can use to install a Microsoft Lync Server 2010 (Release Candidate) Standard Edition server, along with an Edge Server. This document is suited to lab and product evaluation deployments.
Check this out at: http://www.microsoft.com/downloads/en/details.aspx?FamilyID=709d1609-a62a-47bd-baa4-6221dfd3c34c