Loop for show a last item of each category

hi dude
i am newbie in programing and i have idea for put last category item in first page. but my knowledge is poor to complete this solution.
please help me.
this is my idea:

<?php
	wp_list_categories( $args ); ->; category-IDs[len] // put all category ID or slug in to array.
		for ($i=0;$i<=len;++i){
			query_posts('cat=category-IDs[i]&showpost=3');
			include(TEMPLATEPATH . '/inc/loop-thumb.php');
 		}
?>

Thanks