It's in customer/home.tpl.
Code:
<title>{$lng.txt_site_title} {if $main eq "catalog"}
{if $location eq ""} {$lng.txt_subtitle_home}
{else}
{strip}
{section name=position loop=$location start=0 }
{if %position.last% eq "true"} - {$location[position].0|escape}{/if}
{/section}
{/strip}
{/if}
{elseif $main eq "product"}
{if $product.product ne ''} - {$product.product}{/if}
This is a slightly customised title script but the bit you need is {$product.product}. Hope this is what you are looking for.