In the organization where I work, we use E-Groupware for our intranet, we need to integrate it with our extranet which is made in Drupal 6, could do this??? As it would be??? Is exactly what you want users to enter the extranet (Drupal 6) with the same authentication intranet (E-Groupware) and so it used some E-Groupware services on the extranet.
I'm not affiliated with them in any way, just found out that they were using Drupal for this awesome new version of zeit.de.
It was done by iA—although I'm not quite sure whether they took care of the whole thing or just the interaction design.
EDIT:
actually only community.zeit.de is built with Drupal, my bad.
For my customer-security-maniac i've developed small module - HTTP autorization window for admin account.
- User must enter additional login/pasword pair in standard HTTP window when is logged in as admin.
- You can store login and password in database and no need .htaccess and .htpasswd. Thats why it works under IIS too.