There are 2 options to install the latest updates.  I strongly suggest to use the automatic installation because the manual installation will get you busy for at least a couple of hours as you have to install many fixes on different roles and in the correct order!

This article lists the available updates for Microsoft Office Communications Server (OCS) 2007 R2 and specifies the applicability of the updates for each server role.
To install updates for Office Communications Server 2007 R2, use one of the following methods:

Method 1: Cumulative Server Update Installer

To install these updates, you must apply the updates by using Cumulative Server Update Installer, and then manually run the database upgrade from July 2009 for Office Communications Server Back-end database.
Note The Cumulative Server Update Installer applies all updates for the appropriate server role in one click.

Method 2: Manual installation

If you chose to manually install these updates, this article helps you determine the mapping between the updates and the different server roles.

http://support.microsoft.com/kb/968802
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http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=b3b02475-150c-41fa-844a-c10a517040f4