Easy mod, but i'll post it here anyway. If you don't want your sub-forums listed at the top of a main forum listing, just modify the /templates/default/postlist.tpl file as follows:
Find:
That is the beginning of the area to cut out.
Select all text from that line down to:
{* END SUBFORUM LISTING *}
Cut it out and paste below this line:
{if $modlist}{$lang.USER_MOD}: {$modlist}{/if}
This will display your sub-forums below the moderator list for the main forum and just above the 'Display Options'