If sort_inventory is set, items will be
inserted into your inventory in
order by type than alphabetical.  This,
all scrolls will be grouped together,
but in alphabetical order. Same for
all weapons.  This only applies
to new items you pick up - items that 
you are already holding will not be
sorted.

If sort_inventory is not set (default),
items will be inserted via type,
subtype and magic.  This, all axes
will be grouped together in magic
order, all daggers by magic order,
etc.  Unforunately, for scrolls and
rings, new ones just get inserted
last.

If you have a lot of stuff that is not
in alphabetical order but you would
like it to be, the best method is to
drop all of it and then pick it up.