How can I connect an XBox to a new 30-inch Apple Cinema HD Display
M9179LL/A digital flat panel monitor which only accepts a DVI-D connector?

Hold onto your pesos... http://www2.dvigear.com/vitodvisc.html $495
http://www.highway.net.au/parts/converters/4246.html $275
http://www.hotbuyselectronics.com/item_detail.php?item_id=105766 $388.98

best search criteria: NTSC to DVI converter. 

The expense is because Composite is analog and DVI is digital, and the
analog-to-digital converters don't seem to be so popular, yet.

This is a free comment.

if it only has DVI-D input then you are going to need some kinf of
converter to convert the video signal from either composit, s-video,
or component (depending on which adapter you are useing with the xbox)
to DVI-D cause the xbox can only output those three

Another option other then a NTSC to DVI converter is to use a
videocard with DVI out and S-Video in.  As to my knowledge, there are
no moderatly priced video cards with component input.  The ones
offered are more expensive then NTSC to DVI converters.  Purchase the
Xbox HD pack http://www.xbox.com/en-us/hardware/highdefinitionavpack.htm
for $19.99, this allows S-video and compenent outputs from the xbox. 
As to the video card, there are many many options and you can get one
for as little as 150 with the options necessary.  The video card and
computer act as a NTSC to DVI convertor.