Best Practice for Centralized user contact information on a Windows Server Domain

We have a Windows Domain with 250 users, using a Windows 2003 R2 server.  Active Directory contains the updated contact information for our users (email, aliases, addresses, phone numbers).  Our department exists within a much larger organization that maintains the email system, so we don't use Exchange Server.  Each year 50 to 70 people leave our department and an equal number join.

I need to send emails to various groups of users, and maintain and export lists of users and contact information for administrative purposes.  I end up copying all of the contact information from Active Directory into Outlook, because outlook has an easier GUI interface for organizing and exporting contact information and sending email to distribution lists.
This can't be the most efficient way to do things, duplicating information manually in Active Directory and Outlook.  I also don't want to export information using CSVDE or LDIFDE each time changes are made.

I'd like to know how people with more experience organize their personnel information around Active Directory.  Are there popular third party add-ons with these functions?  Or is Exchange Server the usual way of accessing centralized user Contact Information and manipulating distribution lists.

If I get more than one useful answer, I'll split the points between the two best anwers.
Thanks in advance.