Dropdown Select List - Populate with Database Data?

Hey all.

I know how to do something like this with a PHP/Smarty setup, but I just cannot figure it out with Drupal.

So, I have a field called "Authors". I want this field to be populate by the various entries that I have for the "Authors" content type. I know that I need to write some PHP code to make this happen, but I am not sure how to go about it. I need to return a keyed array.

Any help would be appreciated.

Thanks.