How do you create a CCK field that presents a node creator with a list of the website's users? I'm trying to add a CCK field that will present a site manager with a list of instructors which are actually a sub-group of already-authenticated users with the role name of "instructor" for a "class" content type. 

The list of instructors is pretty large, and I'd rather use the actual users that are already on the site to populate that field instead of just having a plain select list.

The "class" content type will have a couple other fields, like location, day of the week, and class type. The problem is figuring out how to add the instructors, who are already authenticated users to the content type via a select list of some kind. Does anyone have any ideas on how to best accomplish this? I can't find a suitable CCK field to do what I'm trying to do, and as mentioned previously, I don't want to use just a text/select list.
You can setup a view for those users and then install Views Field View module. With this module you can add a new field to your node which is a link to that view.

That view will be able to get arguments coming from the node where it's linked from.