http://googleappsupdates.blogspot.com/2008/12/standalone-contact-manager-available.html

It claims that once activated, you'll have a 'Contacts' link in the top-left of your calendar, docs, and sites but I'm not seeing that.

Standalone app (once activated) is at
https://www.google.com/contacts/a/<domain>/

but there's nothing at https://www.google.com/contacts/

It's just the Gmail contacts manager on a separate page apparently.

http://img201.imageshack.us/img201/4103/picture4xz8.png
(Sensitive information edited out of image)