i've got a little list.

Thinking about the "tips" chapter.  Here's the stuff that I can remember offhand, without looking, that we promised/planned we would explain in it:

framebuffer
serial console
kernel compilation (special reference to debugging knobs)
lilo
domu 3d (iffy.  very iffy.  i wonder if the new boxes will have iommu?)
xenbus/xenstore (our example used it _and_ the framebuffer, actually.  it's really cool.  or so I say, but I'm easily impressed.)