For my d6 site, I was wanting to display two different types of nodes both of which are created by users. Not wanting to show my stupidity I searched and searched but couldn't find anything and had previously writter a dynamic filter code for d5 which struck me as messy. Finally, I wrote something for myself that can enable it as a relationship in my code. Thought I'd share it in case other people needed the same code. If there is a simpler way, I'd love to know it but to me this is incredibly simple and shows the power of views2.
function user_relation_views_data(){
$data=array();
$data['node']['uid']['relationship'] = array(
'base' => 'node',
'base field' => 'uid',
'field' => 'uid',
'group' => 'node',
'title' => 'Author Relationship',
'help' => 'Relate nodes by the author',
'handler' => 'views_handler_relationship',
'label' => t('UserID'),
);
return $data;
}