“Office Communications Server 2007 R2 delivers streamlined communications for your users so they can find and communicate with the right person, right now, from the applications they use most (like Office Outlook).  You are able to deliver a variety of software-powered communications solutions, including enterprise telephony, on-premise audio, video, and web conferencing and enterprise instant messaging, while maintaining the operational control required and without expensive infrastructure and network upgrades. And when you download the 180-day trial software, you're automatically registered to receive valuable resources delivered at strategic intervals throughout the software evaluation period.”

http://technet.microsoft.com/en-us/evalcenter/bb684921.aspx