WordPress 2.9 built with new ability to Extend User Contact Info, this tricks can be done by added some code on functions.php in your current theme. We can added many contact info, depend on your needed. To do extend user contact info, open the files and add this code
<?php
function my_new_contactmethods( $contactmethods ) {
// Add Twitter
$contactmethods['twitter'] = 'Twitter';
//add Facebook
$contactmethods['facebook'] = 'Facebook';
return $contactmethods;
}
add_filter('user_contactmethods','my_new_contactmethods',10,1);
?>