Microsoft has posted a 330MB patch for Microsoft Office 2008 for Mac that will update it to version 12.2.8. This update improves stability but also addresses vulnerabilities that can allow an attacker to overwrite your computers memory with malicious code.
They have also rolled 13 previous updates into this one to consolidate everything. Those previous updates range from version 12.1.1 to 12.2.7.
This update applies to the following programs: Office 2008, Office 2008 Home and Student Edition, Office 2008 Special Media Edition, Word 2008, Excel 2008, PowerPoint 2008, Entourage 2008, Office 2008 for Mac Business Edition.
To see more detail on this update you can visit the Description of the Office 2008 for Mac 12.2.8 Update and Microsoft Office 2008 for Mac 12.2.8 Update Download pages.