There's a new update available today for Office 2004 and Office X. For Office 2004, version 11.2.5 fixes vulnerabilities that could be used by a malicious attacker, as well as addresses some Entourage issues. For Office X, version 10.1.7 has updates related to stability and security.
If you use Microsoft AutoUpdate, it will automatically get this update when it next runs. You can manually run Microsoft AutoUpdate by opening any Office:Mac application, selecting the Help menu, then clicking on "Check for Updates". You can also download the update from Mactopia (on the main Mactopia page, look in the right column for the Quick Downlaods).