Can I create a dropdown populated with user logins?

Can I create a dropdown populated with user logins?

Hi
 
Looking through the docs and searching I haven't been able to work out how to do this; I don't think it's been asked before.
 
Is it possible to create a dropdown that is dynamically populated with the login names/emails of users who have access to the application? I'd like someone filling in a form to select from the list of users and the form to fire off an email to the user when the form is submitted with the details of the form (I'm sure I can do this using Deluge but I don't have access to the email address). Am I missing something fundamental; I believe I can fire off an email to the admin or submitting-user but not to another user.
 
I'm guessing this is possible using a static list but ideally I'd like the dropdown to populate with the users that I've permissioned to the application.
 
Any help appreciated.
 
Thanks in advance.