To display further sub-subcategories you could just add a section loop within the existing 'subcat' section loop. This seems a bit convoluted but haven't had time to figure it out properly - there would be a much nicer way to do it in include/categories.php if you were to sort an array properly. But for anyone not bothered, smarty seems to be fast enough to handle doing all these loops...
Code:
{* $Id: categories.tpl,v 1.23 2004/06/24 09:53:29 max Exp $ *}
{capture name=menu}
{if $active_modules.Fancy_Categories ne ""}
{include file="`$fancycategories_config.modules_path`/fancy_categories.tpl"}
{else}
{if $config.General.root_categories eq "Y"}
{section name=cat_num loop=$categories}
<FONT class="CategoriesList">{$categories[cat_num].category}</FONT>
{section name=subcat loop=$allcategories}
{if $allcategories[subcat].parentid eq $categories[cat_num].categoryid}
{$allcategories[subcat].category}
{section name=subsubcat loop=$allcategories}
{if $allcategories[subsubcat].parentid eq $allcategories[subcat].categoryid}
>
{$allcategories[subsubcat].category}
{/if}
{/section}
{/if}
{/section}
{/section}
{else}
{section name=cat_num loop=$subcategories}
<FONT class="CategoriesList">
{$subcategories[cat_num].category}</FONT>
{/section}
{/if}
{/if}
{/capture}
{ include file="menu.tpl" dingbats="dingbats_categorie.gif" menu_title=$lng.lbl_categories menu_content=$smarty.capture.menu }
It's the section loop called 'subsubcat' that adds these categories, with a > infront of the name. This is the only thing I added to do this.