Only one place to remember if you want the latest updates for Communications Server and Clients :)
http://technet.microsoft.com/en-us/office/ocs/ee695846.aspx

The Communications Server Products team periodically releases updates. Find links below to the most recent update information and software for your products.

Servers

Office Communications Server 2007 R2

• Cumulative Updates for Office Communications Server 2007 R2 - October 2009
• Update for OCS 2007 R2 Database – July 2009

Speech Server 2007 R2

• Update for Speech Server 2007 R2 – April 2009

Group Chat Server 2007 R2

• Update for Group Chat Server 2007 R2 – July 2009
• Update for Group Chat Server 2007 R2 Administration Tool - July 2009

Device-based Clients

Office Communicator Phone Edition 2007 R2

• Update for Office Communicator Phone Edition 2007 R2 – October 2009

Office Communicator Mobile 2007 R2

• Update for Office Communicator Mobile 2007 R2 – July 2009

Clients

Office Communicator 2007 R2

• Update for Office Communicator 2007 R2 – October 2009

Office Live Meeting

• Update for Live Meeting 2007 Client – September 2009
• Update for Live Meeting 2007 Conferencing Add-in for Outlook – September 2009

Group Chat Client 2007 R2

• Update for Group Chat Client 2007 R2 – July 2009

Attendant 2007 R2

• Update for Office Communications Server 2007 R2 Attendant – July 2009