functions.php

<?php

/**
 * Update Contact Methods
 *
 * @author Bill Erickson
 * @link http://www.billerickson.net/code/add-remove-contact-methods/
 */
function be_contact_methods( $contactmethods ) {
	$remove = array( 'aim', 'yim', 'jabber' );
	foreach( $remove as $service ) {
		if( isset( $contactmethods[$service] ) ) {
			unset( $contactmethods[$service]);
		}
	}

	$add = array(
		array( 
			'service' => 'linkedin',
			'label' => 'LinkedIn URL',
		),
		array( 
			'service' => 'netvibes',
			'label' => 'Netvibes URL',
		),
		array( 
			'service' => 'twitter',
			'label'  => 'Twitter URL'  
		),
	);
	foreach( $add as $item ) {
		if( !isset( $contactmethods[$item['service']] ) ) {
			$contactmethods[$item['service']] = $item['label'];
		}
	}	

	return $contactmethods;
}
add_filter( 'user_contactmethods', 'be_contact_methods' );