[JWait]

The routine that lists your subcategories is located in skin1/customer/main/subcategories.tpl.

{foreach from=$subcategories item=subcat}
<tr>
{if $tmp and $first_subcat ne "Y"}
	<td valign="top" rowspan="{count value=$subcategories print="Y"}"><img src="{if $current_category.icon_url}{$current_category.icon_url}{else}{$xcart_web_dir}/image.php?id={$cat}&amp;type=C{/if}" alt="" /></td>
{assign var="first_subcat" value="Y"}
{/if}
	<td class="SubcatTitle"><a href="home.php?cat={ $subcat.categoryid }"><font class="ItemsList">{ $subcat.category|escape }</font></a><br /></td>
	<td class="SubcatInfo">{if $config.Appearance.count_products eq "Y"}
{if $subcat.product_count}{ $subcat.product_count } {$lng.lbl_products}
{elseif $subcat.subcategory_count}{ $subcat.subcategory_count } {$lng.lbl_categories|lower}
{/if}
	{/if}</td>
</tr>
{/foreach}

I'm not sure how you would go about breaking it into 2 (or more) columns. Also, looking at your site it appears you don't have enough room to do that anyway as the page would then stretch too wide for most browsers, or worse the text would wrap.