I recently got a request from one of our users at a larger site to be able to have all the staff's contacts in their contact list.
Upon investigating what can be done with simple old Microsoft Outlook and Active Directory I was suitably impressed. What these two enable you to do is to link your Active Directory with the Outlook Address Book. When the user clicks on the "To:" button in Outlook it simply queries your domain controller and brings up a list of all the names and email addresses that it knows about in the base DN that you give it (the top level of the LDAP directory tree is the base, referred to as the "base DN").
How to configure this:
1) Your Windows Server 2000+ is already equipped to do this task so you need to do nothing to it.
2) On the clients do the following:
Click on Tools -> Email Accounts.
Click on "Add a new directory or address book"
Select the LDAP option
Insert your server name (this is the FQDN of your domain controller that you wish to query. Normally your PDC (e.g. myserver.mylan.lan)
Insert some login details of a user with enough rights. The user name has to be entered in the whole cn=xxx,cn=xxx,dc=xxx,dc=xxx fashion.
Click the "More Settings Button"
Enter how you want the directory to appear to the user in the "Display Name" text field.
Click the "Search Tab"
Enter your search base DN which could be something like ou=staff,dc=bla,dc=lan
Done! Now when your clients clicks the address book they can browse the active directory for users to send emails to. Note you must have filed in the user objects "email" field for them to show up by default.