I've begun working on an API reference manual for XPCOM. I'm planning to incorporate it into the upcoming DevMo site. Here's the link to the content I have developed so far:
http://friedfish.homeip.net/~darinf/reference/xpcom/
This is my first time using XSLT to generate HTML docs from XML. I have to say it is incredibly nice, and sooo much easier than hacking HTML directly. The best part is that if my tag choices suck (and I'm sure they do), someone can easily come in and suggest a better XSLT stylesheet :-)