I just came across this.  Should you want to play with our VoIP solution that also integrates into Exchange 2007 then this is for you. 

Microsoft Office Communications Server 2007 Public Beta

Microsoft Office Communications Server 2007 provides users with streamlined real-time communications on an extensible VoIP foundation that provides the operational control your organization requires.

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Featured Resources

Now available: Microsoft Office Communications Server 2007 public beta

• Download Microsoft Office Communications Server 2007 Public Beta with Office Communicator 2007.
• Download the documentation for Office Communications Server 2007 beta

Featured Webcasts
Join us for an overview of Microsoft unified communications solutions and to learn more about Microsoft Office Communications Server 2007.

• Microsoft Unified Communications Overview
• Microsoft Office Communications Server 2007 Overview
• Scenarios for Using Office Communicator 2007

Source: Microsoft Office Communications Server 2007 Public Beta

ttfn

David