Mine

add_filter('search_rewrite_rules', 	'createRewriteRules');
add_filter('query_vars','addQueryVar');

function addQueryVar($wpvar_array) {
	$wpvar_array[] = 'mycustom';
	return($wpvar_array);
}
	
function createRewriteRules($rewrite) {
	global $wp_rewrite;
	
	// add rewrite tokens
	$keytag_token = '%what%';
	$wp_rewrite->add_rewrite_tag($keytag_token, '(.+)', 'mycustom=');
	
	$keywords_structure = $wp_rewrite->root . "mycustom/$keytag_token";
	$keywords_rewrite = $wp_rewrite->generate_rewrite_rules($keywords_structure);
	
	return ( $rewrite + $keywords_rewrite );
}




add_filter('the_content', 'mythecontent');
function mythecontent($content) {
	global $wp_version;
	$what = (isset($wp_version) && ($wp_version >= 2.0)) ? get_query_var('mycustom') : $GLOBALS['mycustom'];
	return $content . $what;
}