Exchange uses Active Directory. So does Outlook. I haven't seen tools to expose AD directly in a SharePoint contacts list, but I suspect that if you ask on a SharePoint group you'll find someone who has some sample code.

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Sue Mosher, Outlook MVP
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> I want to create a gobal address/phone list for employees in a firm that
> should be available from Outlook and Sharepoint Services.
>
> Whats the best solution? Exhange? Active Directory? Other?