After upgrading to Mac OS X 10.6.2 (Snow Leopard) from Mac OS X 10.5.8 (Leopard), I found that the Tahoma font was not displayed by any Office 2004 or Office 2008 application.
Surprisingly, the Tahoma font and many others were at ~/Library/Fonts Disabled instead of being at ~/Library/Fonts.
Just moving all fonts from ~/Library/Fonts Disabled to ~/Library/Fonts fixed the issue.
Additionally, I used Control-click over the fonts in Apple's Font Book utility to resolve duplicates. Finally, I used FontDoctor and Font Finagler to fix any remaining font issues. So far, so good.
[crarko adds: I do recall there being a few font issues after doing the Leopard » Snow Leopard upgrade. I did remind me why I thought Font Book was not a particularly great utility. What has been the experience of others with Font Book and upgrades?]

