[XeTeX] XeTeX documentation? (from "Checking if a font exists")

[Michiel Kamermans]

Jonathan,

> I'm surprised no-one has suggested the straightforward, pure-xetex 
> approach: something along these lines (untested).....
> [snip]

Nice... I didn't know there was a \nullfont command for checking against.

That does bring up a question though: is there a comprehensive pdf 
document or web page that describes the various commands available in 
XeTeX to make life easier? TeX has the TeX book and TeX by Topic, LaTeX 
has fairly large number of publications dedicated to it, where might one 
find something similar for XeTeX? (and if possible, can it be linked to 
from the SIL XeTeX page so it's easy to find?)

- Mike "Pomax" Kamermans
nihongoresources.com