Applications like FaceTime access information stored by Address Book using Apple's Core Data framework. Microsoft has it's own way of storing contact information, and FaceTime won't read it. In order for FaceTime (and other apps) to access your contacts, you need to get the data into Apple's storage container.
Until Microsoft puts Outlook on speaking terms with iCloud, you may use SyncServices to Sync Outlook contacts with the Apple Address Book. From within Outlook:
On the Tools tab, click Sync Services.
In the left pane, select the check box for Contacts.
Under Select the accounts to sync, choose the account or accounts that
you want to sync for the selected item type.
Note The On My Computer account includes all Outlook items that are
not synchronized with a Microsoft Exchange account.
On the Outlook folder to add new items to pop-up menu, choose the
location in Outlook where you want new items to be saved. "New" items
are those that are added first in a different application or device,
and then synced to Outlook.
Close the Sync Services dialog box, and then on the confirmation
message, click OK.
Be certain Outlook is fully up-to-date because there were reports of problems with syncing using earlier versions under OS 10.7 Lion.