Nick, I'm not sure what your original post was asking, but if you're just trying to figure out how to set up a LDAP server, you might want to search the forum and see if you can find a thread I started (and Gary contributed to) on LDAP several months ago.
The bottom line was that you can more or less follow the recipe in the first few chapters in O'Reilly's LDAP book (Amazon or Barnes & Noble will have it). It's not Mac-specific (so doesn't tell you about using NetInfo) -- but the book explains how to install Berkeley DB to set up the database. Pretty much any free articles I found about LDAP were of no help (and in fact served to confuse me rather badly -- that's not hard to do in general, however).
There are some utilities out there for exporting from Mac's address book for easy importing to LDAP. And there are also a few GUI apps for manually entering data. And there's phpLDAPadmin. You'll have to use google to track those down.
And the REAL bottom line was that LDAP disappointed me. I wanted a
universally-accessible editable universal address book for myself (I use Outlook, Thunderbird, Mail.app, SquirrelMail, Address Book, etc etc) -- LDAP provides something kind of half-baked and uneditable from any of those programs, so it didn't serve my purposes. (Though yours may be different!)
(And I suppose I shouldn't blame LDAP alone. Those clients could include LDAP editing if the developers wanted it, I suppose. LDAP, however, is designed as a read-often write-infrequently system -- so maybe my expectations were ill placed to begin with.)