XML-RPC2 and Drupal’s Services Module
Sometimes, there will be a need for you to integrate Drupal content to a non-Drupal content. For instance, the non-Drupal content is in PHP and you want to have the same menu from Drupal to appear on your non-Drupal site. You can do that using the Drupal Services module and using PEAR’s XML-RPC2 Library.
A concise example can be found using this page
The example that was linked does not use the key authentication. However, I would not recommend for you not to use the key authentication so that you can prevent other people accessing the API without your knowledge.
Tags: Drupal