Mac OS X 10.3 Fonts
I love Apple's Knowledge Base, and I'm not afraid to admit it. Sure, sometimes it has seemingly silly articles, and I don't think it is as comprehensive as a certain software company in Redmond's similar offer (though to be fair, Apple has cornered the market on Apple related knowledge base articles.
Lots of Macs users out there are big fans of fonts. They install fonts by the bucket load, and want to get rid of fonts that they aren't using. However, if you delete fonts that ship with the OS wacky things start to happen. Enter Apple Knowledge base article number 25710. It lists all the fonts installed by OS X and, more importantly, which fonts you should never disable.
Happy fonting.