Allowing users to self-register

Does anyone know of a way, or where to modify RT, to allow users to
self-register? I was going to create an account with admin rights and let
them in that way, but I’d rather not expose the entire admin interface.
Basically I am looking to create a way that the only thing the users would
see for this self-registration function is the create user button in the
admin interface.

Ideas?

tia

Justin