This simple snippet will provide you with a HTTP or HTTPS Fully Qualified Domain Name URL and Base Path to your CakePHP installation. I use it for the HTML base tag.
<base href="<?php echo (env('HTTPS') ? 'https://' : 'http://') . env('HTTP_HOST') . $this->webroot; ?>" />
Simpler alternative
There's a simpler alternative in 1.2:
<?php echo Router::url("/", true); >