Office 2008 Font Install
Office 2008 uses a different method for fonts and many fonts are new versions. Office 2008 will install fonts to the /Library/Fonts/Microsoft folder. By being at the root, then all users on the machine have access to them and you don't get Office 2008 putting multiple copies on the machine for each user.
Entourage 2008 now renders and composes using points rather than pixels (as it did in 2004) to improve consistency between Entourage and Safari font display. Due to this change, emails sent between Entourage 2004 and 2008 would have slight discrepancies in font size. more info
The installer will scour /Library/Fonts/ and ~/Library/Fonts/ for fonts with the same name and move them to /Library/Disabled Fonts/ or ~/Library/Disabled Fonts/ depending on where they were found.
If you install Office 2008 then later go back and install Office 2004, Office 2004 installer will not honor the new font location and re-install fonts in it's usual location. If you are using both Office 2008 and 2004 this could be a problem depending on how you installed. Office 2004 can use the new fonts where using the old fonts with 2008 could be problematic. Just be sure to install 2004 BEFORE installing 2008.
Troubelshooting Fonts after installing.
Entourage Default Font Preferences:
Just a quick word about the new fonts. I really like Consolas for plain text readability. The new fonts have also been adjusted for size so you shouldn't see so much change when exchanging mail with PC users.
Descriptions taken from The Next Big Thing in Online Type
Font Facts:
Despite the version number, many (if not all) of the MSFT fonts are newer than the Apple OS ones.
Office 2008 does not need ANY of its fonts to "run." However, various features of Office 2008 will be broken or display poorly unless you leave the fonts it installs in place.
Office 2008 relies on up-to-date Unicode versions of fonts that support ligatures and faces. Its own font set has been updated to provide these capabilities. I would caution you not to disable the Chinese/Japanese fonts. These are required to produce certain special characters.