[lug] Groupware recommendations?

[Ben]

I've got a Debian Etch server providing basic services: file sharing
(samba), imap (dovecot), webmail (squirrelmail), smtp (postfix) and
everything uses ldap to authenticate. Users get their e-mail via
thunderbird (windows) when in the office and webmail or imaps when out
of the office. I was thinking of adding some groupware functionality
when I upgrade to Lenny (when it becomes stable). Specifically, it would
be nice to have shared addressbooks and an addressbook that is the same
in Thunderbird and webmail. Additionally, a shared calendar would be
nice as well. 

Any recommendations?

I looked at zimbra, but I'm intimidated by how big it is and how it
bundles all the services it uses. Since it includes (for example)
postfix, I can't get security updates to postfix from debian / apt-get.
I have all my services configured how I want them (greylisting, rbl
lists, etc) and I don't know how easy it will be to keep / recreate that
with this 'integrated' postfix. Also, can I get all of zimbra to
authenticate against ldap and have samba play nicely with that same ldap
server? Basically, I've got things setup nicely now and don't want to
rock the boat.

I looked at group-office, but was dismayed to learn that it stores all
user passwords in plaintext in its sql database (even if doing external
authentication) -- 
http://www.group-office.com/forum/viewtopic.php?t=4056&highlight=

The Sync Kolab plugin for thunderbird looks like it'll provide some of
the functionality I'm looking for. Same for the Lightning plugin for
thunderbird. Maybe run SyncML server?

Also, anyone know of the status of ldap write for addressbooks in
Thunderbird 3?

Any ideas or recommendations appreciated!

Ben

Ben