Shared address book for Outlook?

[Randy Orrison <randy@orrison.com>]

I'm looking for software to set up a shared address book (names, email 
addresses, postal addressess, telephone numbers, etc) that can be used 
by Outlook and Outlook Express.  I suspect that ldap will be a part of 
the solution, but haven't found a simple way of setting up and editing 
the address book.  Ideally I'd like a web-based interface that would 
allow creation of new entries and modification of existing entries.  Is 
there such a package?  (Not that it matters, but I'm running fetchmail / 
exim / courier-imap and pop3.)

(Don't suggest changing the clients, I was lucky to get a linux server; 
we're almost exclusively Microsoft.)

Thanks,

Randy Orrison