If I ever get LDAP working I will want to disable the creation of new users. How would I go about doing this?

Set:

$wgLDAPUseLocal = false; #should be the default

After you switch to LDAP, the only users that can create an account are those who have an LDAP account. If you want to restrict how accounts are created, you should be able to use the normal methods mediawiki would use by default.

V/r,

Ryan Lane