Microsoft recently released the "Agent Communications Panel for Microsoft Dynamics CRM 4.0" which provides an out-of-the-box integration with Office Communications Server for call center functionality within CRM.
"The Agent Communications Panel for Microsoft Dynamics
CRM 4.0 is an application add-in to Microsoft Dynamics CRM 4.0. It works with
Microsoft Dynamics CRM and Microsoft Office Communications Server 2007 R2, and
enables agents to manage their communications (make calls, receive calls,
conference, and chat) from their Microsoft Dynamics CRM system. The Agent
Communications Panel is an XAML browser application (XBAP). It is published to a
Web server and opened from a Web browser."
I haven't had a chance to set it up and play with it yet, but it looks like it's a logical extension to CRM that should be well-received. You can download it here.