This doesn't need a huge explanation, we were looking to redirect a single node to an external site.
I used to do this by placing a response.redirect in an asp file.

One way I got this done today was in the Drupal template_preprocess.

In your theme's template.php,

function themename_preprocess(&$variables, $hook){
if ($variables['node']->title == 'Target Title'){

Just swap out the themename, Target Title, and the, and you should be good to go.