johndugan

function is_blog () {
	global  $post;
	$posttype = get_post_type($post );
	return ( ((is_archive()) || (is_author()) || (is_category()) || (is_home()) || (is_tag())) && ( $posttype == 'post')  );
}


Usage: 

 <?php if (is_blog()) { echo 'You are on a blog page'; } ?>