Add "Company" field to WordPress user account and add sortable company column to the user backend.

functions.php

//add&remove field from user profiles - sorce:http://davidwalsh.name/add-profile-fields
function modify_contact_methods($profile_fields) {

	// Add new fields
	$profile_fields['company'] = 'Company';

	// Remove old fields
	//unset($profile_fields['aim']);

	return $profile_fields;
}
add_filter('user_contactmethods', 'modify_contact_methods');

//Add the colum to the user backend
function user_sortable_columns( $columns ) {
	$columns['company'] = 'Company';
	return $columns;
}
add_filter( 'manage_users_sortable_columns', 'user_sortable_columns' );

//alter the user query and sorts whole list by company
function status_order_in_user_query($query){
	if('Company'==$query->query_vars['orderby']) {
		$query->query_from .= " LEFT JOIN wp_usermeta ON wp_users.ID = wp_usermeta.user_id AND meta_key = 'company'";
		$query->query_orderby = " ORDER BY wp_usermeta.meta_value ".($query->query_vars["order"] == "ASC" ? "asc " : "desc ");//set sort order
	}
}
add_action('pre_user_query', 'status_order_in_user_query');

//makes the user meta searchable and returen results- source: http://www.tomauger.com/2012/tips-and-tricks/expanded-user-search-in-wordpress
function extended_user_search( $user_query ){
	// Make sure this is only applied to user search
	if ( $user_query->query_vars['search'] ){
		$search = trim( $user_query->query_vars['search'], '*' );
		if ( $_REQUEST['s'] == $search ){
			global $wpdb;
			$user_query->query_from .= " JOIN wp_usermeta ON wp_users.ID = wp_usermeta.user_id";
			$user_query->query_where = 'WHERE 1=1' . $user_query->get_search_sql( $search, array( 'user_login', 'user_email', 'user_nicename', 'meta_value' ), 'both' );
		}
	}
}
add_action( 'pre_user_query', 'extended_user_search' );

//add columns to User panel list page
function add_user_columns( $defaults ) {
     $defaults['company'] = __('Company', 'user-column');
     return $defaults;
}
add_filter('manage_users_columns', 'add_user_columns', 15, 1);

//Print the user data in the new column
function add_custom_user_columns($value, $column_name, $id) {
      if( $column_name == 'company' ) {
		return get_the_author_meta( 'company', $id );
      }
}
add_action('manage_users_custom_column', 'add_custom_user_columns', 15, 3);