The SitePoint PHP blog has posted a new Drupal tutorial about allowing multiple editors to work on the same node of content.

have encountered a practical use case where the default configuration options are not enough. Namely, if you need to have multiple users with access to edit a particular node of a given type but without them necessarily having access to edit others of the same type. In other words, the next great article should be editable by Laura and Glenn but not by their colleagues. However, out of the box, users of a particular role can be masters either of their own content or of all content of a certain type. So this is not immediately possible. In this article I am going to show you my solution to this problem in the form of a simple custom module called editor_list.

He walks you through the process, first creating the .info file needed to define the module and the changes needed for the .module file. He creates a few helper functions to get the editor listing for a node and its matching access rules. With the module created he then gets into building the fields, again making helper methods to get the editors for the fields. Finally he "tidies up" and adds an "Authored on" section to the node editor with a helper function to receive and handle the results of this field when the form is submitted.