Protecting systems from Word's zero-day vulnerabilities

What steps can I take to protect my systems from zero-day vulnerabilities in Microsoft Word?

Microsoft recommends not opening suspicious Word documents from untrusted sources. This is always good advice but can be difficult to implement successfully given the level of business correspondence delivered as Word documents and the ease with which e-mail addresses can be spoofed. Patches do not appear to be scheduled for release until January at the earliest.

One option for home users is to switch to the OpenOffice suite (free from OpenOffice.org). Business users may want to accelerate their plans to upgrade to Office 2007, which reportedly is not vulnerable. IT departments may want to make sure they are deploying desktops under a least-privilege security model rather than giving desktop users local administrative rights. This can slow the code-dropping payloads in infected documents, as they may not be able to infect the registry without administrative access. The best defense is a tightly restricted outbound firewall on the desktop systems configured to block everything that is not expressly permitted.

Being prompted for every new outbound connection is annoying but can be effective in identifying when your computer suddenly wants to talk to a new server on a new port number.