Enrolling External Students - Moodle

[barney]

If you were thinking about making a course available to students in other institutions as well as your own I'd be interested to know how you go'd about it and the reasons for your choice.
I think the 2 viable options are to create an external enrollment database, create the enrollments in there and match it to the Moodle course.
You could conceivably create AD accounts for your external users so they could enrol themselves (assuming LDAP authentication is turned on)
Are there other ways of doing it?

In an ideal world I guess I'd like to be able to create and advertise a course. Send the enrolment key to other institutions involved (to stop any old tom dick or harry's enrolling) and forcing them to use their school e-mail address for uniformity. Does this make sense and more importantly is is possible?

[CyberNerd]

does moodle network help here?
Moodle Network - MoodleDocs

[barney]

does moodle network help here?
Moodle Network - MoodleDocs

I looked at that but our partner schools are unlikely to be Moodle sites