I got the mouse and CD-ROM working.  Thanks especially to Manuel Bouyer, who
gave me the pointers that got me to the right part of the ATAPI code.

http://www.plethora.net/~seebs/vpcbsd.png

is a screenshot (1024x768) showing VirtualPC on my Mac... running NetBSD.
uname -a and df output, including /dev/cd0a.

I picked WindowMaker, on the grounds that anything that takes five hours to
compile is clearly a demonstration of a healthy system.

If you're curious, it's quite substantially slower than my PII-233 laptop,
even though it's a G3-400.

Anyone who wants to help track down and defeat the remaining issues is
welcome.  ;)

-s