Restrict Admin Menu Items by Username in WordPress

You can hide specific admin menu items from a specific user in the WordPress dashboard. Replace username with the login of the user you want to hide those menu items from:

function remove_menus()
{
    global $menu;
    global $current_user;
    get_currentuserinfo();

    if($current_user->user_login == 'username')
    {
        $restricted = array(__('Posts'),
                            __('Media'),
                            __('Links'),
                            __('Pages'),
                            __('Comments'),
                            __('Appearance'),
                            __('Plugins'),
                            __('Users'),
                            __('Tools'),
                            __('Settings')
        );
        end ($menu);
        while (prev($menu)) {
            $value = explode(' ',$menu[key($menu)][0]);
            if(in_array($value[0] != NULL ? $value[0] : "" , $restricted)) {
                unset($menu[key($menu)]);
            }
        } // end while

    } // end if
}
add_action('admin_menu', 'remove_menus');

This uses a WordPress hook. Learn more in WordPress Hooks Explained.