wordpress admin plugin menu custom css

Use the admin_head hook and just echo out what you need to:

function my_admin_head() {
    // Custom Style
    echo '<link rel="stylesheet" href="'.WP_PLUGIN_DIR.'/style.css" type="text/css" />';

    // Our JS
    echo '<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js"></script>';

}
add_action('admin_head', 'my_admin_head');