Microsoft Office Communicator 2005 is an enterprise messenger that integrates communications capabilities (including instant messaging, rich presence, PC-based voice and video, Voice over Internet Protocol (VoIP), and enterprise telephony) with productivity and other communications applications. http://www.microsoft.com/office/rtc/client.mspx

the 120 day trial download of the final version is now available for download http://www.microsoft.com/downloads/details.aspx?familyid=9253DBEA-CC4F-4934-B35D-E2C90B6406DB&displaylang=en

 

Office Communicator is the best client for Live Communications Server (download the LCS 2005 SP1 trial) http://www.microsoft.com/downloads/details.aspx?familyid=F638E94A-7CDF-4E42-B286-080240FCBCCB&displaylang=en

 

Cool new IM client for business, loads of new features over and above Windows Messenger without the cluttered neon flashing lights :) of MSN Messenger 7 http://messenger.msn.com/Download